AirflowException "AppBuilder is not initialized" on startup with FAB provider 3.5.0

### Apache Airflow Provider(s)

fab

### Versions of Apache Airflow Providers

/opt/airflow$ pip freeze | grep providers
apache-airflow-providers-amazon==9.22.0
apache-airflow-providers-celery==3.17.0
apache-airflow-providers-cncf-kubernetes==10.13.0
apache-airflow-providers-common-compat==1.14.0
apache-airflow-providers-common-io==1.7.1
apache-airflow-providers-common-messaging==2.0.2
apache-airflow-providers-common-sql==1.32.0
apache-airflow-providers-docker==4.5.2
apache-airflow-providers-elasticsearch==6.5.0
apache-airflow-providers-fab==3.5.0
apache-airflow-providers-ftp==3.14.1
apache-airflow-providers-git==0.2.4
apache-airflow-providers-google==20.0.0
apache-airflow-providers-grpc==3.9.2
apache-airflow-providers-hashicorp==4.5.0
apache-airflow-providers-http==6.0.0
apache-airflow-providers-microsoft-azure==13.0.0
apache-airflow-providers-mysql==6.5.0
apache-airflow-providers-odbc==4.12.0
apache-airflow-providers-openlineage==2.11.0
apache-airflow-providers-postgres==6.6.0
apache-airflow-providers-redis==4.4.2
apache-airflow-providers-sendgrid==4.2.1
apache-airflow-providers-sftp==5.7.0
apache-airflow-providers-slack==9.7.0
apache-airflow-providers-smtp==2.4.2
apache-airflow-providers-snowflake==6.10.0
apache-airflow-providers-ssh==4.3.1
apache-airflow-providers-standard==1.12.0

### Apache Airflow version

3.1.8

### Operating System

Debian GNU/Linux 12 (bookworm)

### Deployment

Official Apache Airflow Helm Chart

### Deployment details

Use apache/airflow:3.1.8-python3.12 image


### What happened

When running Airflow 3.1.8 with `apache-airflow-providers-fab==3.5.0` (using Python 3.12), the application fails to handle login requests and throws a 500 Internal Server Error. 

Looking at the traceback, it crashes with `airflow.exceptions.AirflowException: AppBuilder is not initialized.` during the FastAPI endpoint execution (`/auth/token` or login routes). 

I think the error occurs because `auth_manager.register_views()` is called, which in turn calls `self.security_manager`. However, because the `AppBuilder` initialization context is not yet fully completed, the `security_manager` property raises the exception.

**Traceback snippet:**
logs in api-server
```python
INFO:     172.32.14.123:56178 - "POST /auth/token HTTP/1.1" 500 Internal Server Error
ERROR:    Exception in ASGI application
  + Exception Group Traceback (most recent call last):
  |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/_utils.py", line 79, in collapse_excgroups
  |     yield
  |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/base.py", line 183, in __call__
  |     async with anyio.create_task_group() as task_group:
  |                ^^^^^^^^^^^^^^^^^^^^^^^^^
  |   File "/home/airflow/.local/lib/python3.12/site-packages/anyio/_backends/_asyncio.py", line 783, in __aexit__
  |     raise BaseExceptionGroup(
  | ExceptionGroup: unhandled errors in a TaskGroup (1 sub-exception)
  +-+---------------- 1 ----------------
    | Traceback (most recent call last):
    |   File "/home/airflow/.local/lib/python3.12/site-packages/uvicorn/protocols/http/httptools_impl.py", line 416, in run_asgi
    |     result = await app(  # type: ignore[func-returns-value]
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |   File "/home/airflow/.local/lib/python3.12/site-packages/fastapi/applications.py", line 1082, in __call__
    |     await super().__call__(scope, receive, send)
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/applications.py", line 113, in __call__
    |     await self.middleware_stack(scope, receive, send)
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/errors.py", line 186, in __call__
    |     raise exc
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/errors.py", line 164, in __call__
    |     await self.app(scope, receive, _send)
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/cors.py", line 85, in __call__
    |     await self.app(scope, receive, send)
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/gzip.py", line 29, in __call__
    |     await responder(scope, receive, send)
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/gzip.py", line 130, in __call__
    |     await super().__call__(scope, receive, send)
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/gzip.py", line 46, in __call__
    |     await self.app(scope, receive, self.send_with_compression)
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/base.py", line 189, in __call__
    |     raise app_exc
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/base.py", line 144, in coro
    |     await self.app(scope, receive_or_disconnect, send_no_error)
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/exceptions.py", line 63, in __call__
    |     await wrap_app_handling_exceptions(self.app, conn)(scope, receive, send)
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
    |     raise exc
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/_exception_handler.py", line 42, in wrapped_app
    |     await app(scope, receive, sender)
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/routing.py", line 716, in __call__
    |     await self.middleware_stack(scope, receive, send)
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/routing.py", line 736, in app
    |     await route.handle(scope, receive, send)
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/routing.py", line 462, in handle
    |     await self.app(scope, receive, send)
    |   File "/home/airflow/.local/lib/python3.12/site-packages/fastapi/applications.py", line 1082, in __call__
    |     await super().__call__(scope, receive, send)
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/applications.py", line 113, in __call__
    |     await self.middleware_stack(scope, receive, send)
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/errors.py", line 186, in __call__
    |     raise exc
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/errors.py", line 164, in __call__
    |     await self.app(scope, receive, _send)
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/base.py", line 182, in __call__
    |     with recv_stream, send_stream, collapse_excgroups():
    |                                    ^^^^^^^^^^^^^^^^^^^^
    |   File "/usr/python/lib/python3.12/contextlib.py", line 158, in __exit__
    |     self.gen.throw(value)
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/_utils.py", line 85, in collapse_excgroups
    |     raise exc
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/base.py", line 184, in __call__
    |     response = await self.dispatch_func(request, call_next)
    |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |   File "/home/airflow/.local/lib/python3.12/site-packages/airflow/providers/fab/auth_manager/fab_auth_manager.py", line 232, in cleanup_session_middleware
    |     response = await call_next(request)
    |                ^^^^^^^^^^^^^^^^^^^^^^^^
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/base.py", line 159, in call_next
    |     raise app_exc
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/base.py", line 144, in coro
    |     await self.app(scope, receive_or_disconnect, send_no_error)
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/exceptions.py", line 63, in __call__
    |     await wrap_app_handling_exceptions(self.app, conn)(scope, receive, send)
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
    |     raise exc
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/_exception_handler.py", line 42, in wrapped_app
    |     await app(scope, receive, sender)
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/routing.py", line 716, in __call__
    |     await self.middleware_stack(scope, receive, send)
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/routing.py", line 736, in app
    |     await route.handle(scope, receive, send)
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/routing.py", line 290, in handle
    |     await self.app(scope, receive, send)
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/routing.py", line 78, in app
    |     await wrap_app_handling_exceptions(app, request)(scope, receive, send)
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
    |     raise exc
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/_exception_handler.py", line 42, in wrapped_app
    |     await app(scope, receive, sender)
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/routing.py", line 75, in app
    |     response = await f(request)
    |                ^^^^^^^^^^^^^^^^
    |   File "/home/airflow/.local/lib/python3.12/site-packages/fastapi/routing.py", line 308, in app
    |     raw_response = await run_endpoint_function(
    |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |   File "/home/airflow/.local/lib/python3.12/site-packages/fastapi/routing.py", line 221, in run_endpoint_function
    |     return await run_in_threadpool(dependant.call, **values)
    |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |   File "/home/airflow/.local/lib/python3.12/site-packages/starlette/concurrency.py", line 38, in run_in_threadpool
    |     return await anyio.to_thread.run_sync(func)
    |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |   File "/home/airflow/.local/lib/python3.12/site-packages/anyio/to_thread.py", line 63, in run_sync
    |     return await get_async_backend().run_sync_in_worker_thread(
    |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |   File "/home/airflow/.local/lib/python3.12/site-packages/anyio/_backends/_asyncio.py", line 2502, in run_sync_in_worker_thread
    |     return await future
    |            ^^^^^^^^^^^^
    |   File "/home/airflow/.local/lib/python3.12/site-packages/anyio/_backends/_asyncio.py", line 986, in run
    |     result = context.run(func, *args)
    |              ^^^^^^^^^^^^^^^^^^^^^^^^
    |   File "/home/airflow/.local/lib/python3.12/site-packages/airflow/providers/fab/auth_manager/api_fastapi/routes/login.py", line 48, in create_token
    |     with get_application_builder():
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^
    |   File "/usr/python/lib/python3.12/contextlib.py", line 137, in __enter__
    |     return next(self.gen)
    |            ^^^^^^^^^^^^^^
    |   File "/home/airflow/.local/lib/python3.12/site-packages/airflow/providers/fab/auth_manager/cli_commands/utils.py", line 69, in get_application_builder
    |     yield _return_appbuilder(flask_app, db)
    |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |   File "/home/airflow/.local/lib/python3.12/site-packages/airflow/providers/fab/auth_manager/cli_commands/utils.py", line 45, in _return_appbuilder
    |     init_appbuilder(app, enable_plugins=False)
    |   File "/home/airflow/.local/lib/python3.12/site-packages/airflow/providers/fab/www/extensions/init_appbuilder.py", line 606, in init_appbuilder
    |     return AirflowAppBuilder(
    |            ^^^^^^^^^^^^^^^^^^
    |   File "/home/airflow/.local/lib/python3.12/site-packages/airflow/providers/fab/www/extensions/init_appbuilder.py", line 159, in __init__
    |     self.init_app(app, session)
    |   File "/home/airflow/.local/lib/python3.12/site-packages/airflow/providers/fab/www/extensions/init_appbuilder.py", line 215, in init_app
    |     self._add_admin_views()
    |   File "/home/airflow/.local/lib/python3.12/site-packages/airflow/providers/fab/www/extensions/init_appbuilder.py", line 311, in _add_admin_views
    |     auth_manager.register_views()
    |   File "/home/airflow/.local/lib/python3.12/site-packages/airflow/providers/fab/auth_manager/fab_auth_manager.py", line 599, in register_views
    |     self.security_manager.register_views()
    |     ^^^^^^^^^^^^^^^^^^^^^
    |   File "/usr/python/lib/python3.12/functools.py", line 998, in __get__
    |     val = self.func(instance)
    |           ^^^^^^^^^^^^^^^^^^^
    |   File "/home/airflow/.local/lib/python3.12/site-packages/airflow/providers/fab/auth_manager/fab_auth_manager.py", line 578, in security_manager
    |     raise AirflowException("AppBuilder is not initialized.")
    | airflow.exceptions.AirflowException: AppBuilder is not initialized.
    +------------------------------------

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/airflow/.local/lib/python3.12/site-packages/uvicorn/protocols/http/httptools_impl.py", line 416, in run_asgi
    result = await app(  # type: ignore[func-returns-value]
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/airflow/.local/lib/python3.12/site-packages/fastapi/applications.py", line 1082, in __call__
    await super().__call__(scope, receive, send)
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/applications.py", line 113, in __call__
    await self.middleware_stack(scope, receive, send)
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/errors.py", line 186, in __call__
    raise exc
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/errors.py", line 164, in __call__
    await self.app(scope, receive, _send)
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/cors.py", line 85, in __call__
    await self.app(scope, receive, send)
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/gzip.py", line 29, in __call__
    await responder(scope, receive, send)
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/gzip.py", line 130, in __call__
    await super().__call__(scope, receive, send)
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/gzip.py", line 46, in __call__
    await self.app(scope, receive, self.send_with_compression)
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/base.py", line 189, in __call__
    raise app_exc
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/base.py", line 144, in coro
    await self.app(scope, receive_or_disconnect, send_no_error)
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/exceptions.py", line 63, in __call__
    await wrap_app_handling_exceptions(self.app, conn)(scope, receive, send)
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
    raise exc
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/_exception_handler.py", line 42, in wrapped_app
    await app(scope, receive, sender)
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/routing.py", line 716, in __call__
    await self.middleware_stack(scope, receive, send)
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/routing.py", line 736, in app
    await route.handle(scope, receive, send)
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/routing.py", line 462, in handle
    await self.app(scope, receive, send)
  File "/home/airflow/.local/lib/python3.12/site-packages/fastapi/applications.py", line 1082, in __call__
    await super().__call__(scope, receive, send)
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/applications.py", line 113, in __call__
    await self.middleware_stack(scope, receive, send)
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/errors.py", line 186, in __call__
    raise exc
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/errors.py", line 164, in __call__
    await self.app(scope, receive, _send)
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/base.py", line 182, in __call__
    with recv_stream, send_stream, collapse_excgroups():
                                   ^^^^^^^^^^^^^^^^^^^^
  File "/usr/python/lib/python3.12/contextlib.py", line 158, in __exit__
    self.gen.throw(value)
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/_utils.py", line 85, in collapse_excgroups
    raise exc
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/base.py", line 184, in __call__
    response = await self.dispatch_func(request, call_next)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/airflow/.local/lib/python3.12/site-packages/airflow/providers/fab/auth_manager/fab_auth_manager.py", line 232, in cleanup_session_middleware
    response = await call_next(request)
               ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/base.py", line 159, in call_next
    raise app_exc
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/base.py", line 144, in coro
    await self.app(scope, receive_or_disconnect, send_no_error)
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/middleware/exceptions.py", line 63, in __call__
    await wrap_app_handling_exceptions(self.app, conn)(scope, receive, send)
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
    raise exc
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/_exception_handler.py", line 42, in wrapped_app
    await app(scope, receive, sender)
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/routing.py", line 716, in __call__
    await self.middleware_stack(scope, receive, send)
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/routing.py", line 736, in app
    await route.handle(scope, receive, send)
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/routing.py", line 290, in handle
    await self.app(scope, receive, send)
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/routing.py", line 78, in app
    await wrap_app_handling_exceptions(app, request)(scope, receive, send)
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
    raise exc
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/_exception_handler.py", line 42, in wrapped_app
    await app(scope, receive, sender)
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/routing.py", line 75, in app
    response = await f(request)
               ^^^^^^^^^^^^^^^^
  File "/home/airflow/.local/lib/python3.12/site-packages/fastapi/routing.py", line 308, in app
    raw_response = await run_endpoint_function(
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/airflow/.local/lib/python3.12/site-packages/fastapi/routing.py", line 221, in run_endpoint_function
    return await run_in_threadpool(dependant.call, **values)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/airflow/.local/lib/python3.12/site-packages/starlette/concurrency.py", line 38, in run_in_threadpool
    return await anyio.to_thread.run_sync(func)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/airflow/.local/lib/python3.12/site-packages/anyio/to_thread.py", line 63, in run_sync
    return await get_async_backend().run_sync_in_worker_thread(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/airflow/.local/lib/python3.12/site-packages/anyio/_backends/_asyncio.py", line 2502, in run_sync_in_worker_thread
    return await future
           ^^^^^^^^^^^^
  File "/home/airflow/.local/lib/python3.12/site-packages/anyio/_backends/_asyncio.py", line 986, in run
    result = context.run(func, *args)
             ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/airflow/.local/lib/python3.12/site-packages/airflow/providers/fab/auth_manager/api_fastapi/routes/login.py", line 48, in create_token
    with get_application_builder():
         ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/python/lib/python3.12/contextlib.py", line 137, in __enter__
    return next(self.gen)
           ^^^^^^^^^^^^^^
  File "/home/airflow/.local/lib/python3.12/site-packages/airflow/providers/fab/auth_manager/cli_commands/utils.py", line 69, in get_application_builder
    yield _return_appbuilder(flask_app, db)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/airflow/.local/lib/python3.12/site-packages/airflow/providers/fab/auth_manager/cli_commands/utils.py", line 45, in _return_appbuilder
    init_appbuilder(app, enable_plugins=False)
  File "/home/airflow/.local/lib/python3.12/site-packages/airflow/providers/fab/www/extensions/init_appbuilder.py", line 606, in init_appbuilder
    return AirflowAppBuilder(
           ^^^^^^^^^^^^^^^^^^
  File "/home/airflow/.local/lib/python3.12/site-packages/airflow/providers/fab/www/extensions/init_appbuilder.py", line 159, in __init__
    self.init_app(app, session)
  File "/home/airflow/.local/lib/python3.12/site-packages/airflow/providers/fab/www/extensions/init_appbuilder.py", line 215, in init_app
    self._add_admin_views()
  File "/home/airflow/.local/lib/python3.12/site-packages/airflow/providers/fab/www/extensions/init_appbuilder.py", line 311, in _add_admin_views
    auth_manager.register_views()
  File "/home/airflow/.local/lib/python3.12/site-packages/airflow/providers/fab/auth_manager/fab_auth_manager.py", line 599, in register_views
    self.security_manager.register_views()
    ^^^^^^^^^^^^^^^^^^^^^
  File "/usr/python/lib/python3.12/functools.py", line 998, in __get__
    val = self.func(instance)
          ^^^^^^^^^^^^^^^^^^^
  File "/home/airflow/.local/lib/python3.12/site-packages/airflow/providers/fab/auth_manager/fab_auth_manager.py", line 578, in security_manager
    raise AirflowException("AppBuilder is not initialized.")
airflow.exceptions.AirflowException: AppBuilder is not initialized.
```

Workaround:
~I found that setting `AIRFLOW__FAB__UPDATE_FAB_PERMS=False` bypasses this issue and allows the server to run successfully.~

### What you think should happen instead

~The FastAPI application should initialize successfully and serve auth requests without crashing, even when the default configuration `update_fab_perms = True` is used.~

~The internal startup sequence should be fixed so that the `AppBuilder` is completely instantiated and attached to the context *before* the Auth Manager attempts to access `self.security_manager` to sync roles or register views.~

### How to reproduce

1. Set up an environment with Airflow 3.1.8 and Python 3.12.
2. Install the FAB provider version 3.5.0: `pip install apache-airflow-providers-fab==3.5.0`
3. Ensure the default configuration for FAB permissions is active (do NOT set `update_fab_perms = False`).
4. Start the Airflow webserver (FastAPI application).
5. Attempt to hit the login route or `/auth/token` endpoint.
6. Observe the `AppBuilder is not initialized` exception in the api-server logs.

### Anything else

Related? https://github.com/apache/airflow/issues/61108

### Are you willing to submit PR?

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### Code of Conduct

- [x] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)


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AirflowException "AppBuilder is not initialized" on startup with FAB provider 3.5.0 #64151

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AirflowException "AppBuilder is not initialized" on startup with FAB provider 3.5.0 #64151

Description

Apache Airflow Provider(s)

Versions of Apache Airflow Providers

Apache Airflow version

Operating System

Deployment

Deployment details

What happened

What you think should happen instead

How to reproduce

Anything else

Are you willing to submit PR?

Code of Conduct

Metadata

Metadata

Assignees

Labels

Type

Fields

Projects

Milestone

Relationships

Development

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