Describe the bug

Values inside the compose file are currently not interpolated from the (default) .env file.

How to reproduce

.env:

KEY1=value1
KEY2=value2

compose.yaml:

services:
  test:
    image: alpine:3.20
    command:
      - sh
      - -c
      - |
        echo ${KEY1}
        sleep 1d

Now when doing:

uc deploy -f compose.yaml  --yes --recreate

...it throws:

WARN[0000] The "KEY1" variable is not set. Defaulting to a blank string. 
Deployment plan:
...

And the container's output is empty (the command becomes just "echo ").

Expected behavior

Similar to docker compose behavior, uncloud should render the configuration with the interpolated variable from .env file:

There should be no warning, and the container's output should be "value1".

Environment:

• Uncloud versions: latest master (dc56917)
• OS version (uname -a): Linux XXX 6.8.0-79-generic #79-Ubuntu SMP PREEMPT_DYNAMIC Tue Aug 12 14:42:46 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux

Notes:

The behavior of interpolating environment variables should mirror the behavior of docker compose IMO