…25658)

## Description 
- Add `MultisigSignature` variant to the `SignatureScheme` GraphQL union
- Introduce `MultisigMemberSignature` (flat struct with
`MultisigMemberSignatureScheme` enum), `MultisigCommittee`,
`MultisigMember`, and `MultisigMemberPublicKey` (union) types
- `MultisigMemberPublicKey` uses a union with `ZkLoginPublicIdentifier`
(exposing `iss` + `addressSeed`) since it's structurally different from
other key types
- `MultiSigLegacy` is converted to `MultiSig` via `TryFrom` to reuse a
single code path
- ZkLogin public identifier conversion follows the same approach as gRPC
(`rpc_proto_conversions.rs:1620`) — going through `sui_sdk_types`

## Test plan 

How did you test the new or updated feature?

- Unit test

---

## Stack
- #25657 
- #25658 <-
- #25659 

## Release notes

Check each box that your changes affect. If none of the boxes relate to
your changes, release notes aren't required.

For each box you select, include information after the relevant heading
that describes the impact of your changes that a user might notice and
any actions they must take to implement updates.

- [ ] Protocol: 
- [ ] Nodes (Validators and Full nodes): 
- [ ] gRPC:
- [ ] JSON-RPC: 
- [ ] GraphQL: 
- [ ] CLI: 
- [ ] Rust SDK:
- [ ] Indexing Framework:

…1/n] (#25657)

## Description 

- Convert `user_signature.rs` into a `user_signature/` module directory
to support upcoming submodules for complex signature types
- Add a `SignatureScheme` GraphQL union type with `Ed25519Signature`,
`Secp256k1Signature`, and `Secp256r1Signature` variants, each exposing
parsed `signature` and `publicKey` fields

## Test plan 

How did you test the new or updated feature?

- Unit test

---

## Stack
- #25657 <-
- #25658
- #25659 

## Release notes

Check each box that your changes affect. If none of the boxes relate to
your changes, release notes aren't required.

For each box you select, include information after the relevant heading
that describes the impact of your changes that a user might notice and
any actions they must take to implement updates.

- [ ] Protocol: 
- [ ] Nodes (Validators and Full nodes): 
- [ ] gRPC:
- [ ] JSON-RPC: 
- [x] GraphQL: Introduce a new union `SignatureScheme` for
`UserSignature`
- [ ] CLI: 
- [ ] Rust SDK:
- [ ] Indexing Framework:

…1/n] (MystenLabs#25657)

## Description 

- Convert `user_signature.rs` into a `user_signature/` module directory
to support upcoming submodules for complex signature types
- Add a `SignatureScheme` GraphQL union type with `Ed25519Signature`,
`Secp256k1Signature`, and `Secp256r1Signature` variants, each exposing
parsed `signature` and `publicKey` fields

## Test plan 

How did you test the new or updated feature?

- Unit test

---

## Stack
- MystenLabs#25657 <-
- MystenLabs#25658
- MystenLabs#25659 

## Release notes

Check each box that your changes affect. If none of the boxes relate to
your changes, release notes aren't required.

For each box you select, include information after the relevant heading
that describes the impact of your changes that a user might notice and
any actions they must take to implement updates.

- [ ] Protocol: 
- [ ] Nodes (Validators and Full nodes): 
- [ ] gRPC:
- [ ] JSON-RPC: 
- [x] GraphQL: Introduce a new union `SignatureScheme` for
`UserSignature`
- [ ] CLI: 
- [ ] Rust SDK:
- [ ] Indexing Framework:

…ystenLabs#25659)

## Description 

- Add `ZkLoginSignature` variant exposing `maxEpoch` and the inner
`userSignature`
- Add `PasskeySignature` variant exposing `authenticatorData`,
`clientDataJson`, and the inner `userSignature`

## Test plan 

How did you test the new or updated feature?

- Unit test

---

## Stack
- MystenLabs#25657 
- MystenLabs#25658 
- MystenLabs#25659 <-

## Release notes

Check each box that your changes affect. If none of the boxes relate to
your changes, release notes aren't required.

For each box you select, include information after the relevant heading
that describes the impact of your changes that a user might notice and
any actions they must take to implement updates.

- [ ] Protocol: 
- [ ] Nodes (Validators and Full nodes): 
- [ ] gRPC:
- [ ] JSON-RPC: 
- [ ] GraphQL: 
- [ ] CLI: 
- [ ] Rust SDK:
- [ ] Indexing Framework:

#25696)

## Description 

- Add `inputs`, `publicIdentifier`, and `jwkId` fields to
`ZkLoginSignature` to match the gRPC interface

## Test plan 

How did you test the new or updated feature?
`cargo check -p sui-indexer-alt-graphql`

---

## Stack
- #25657 
- #25658 
- #25659
- #25696 <-

## Release notes

Check each box that your changes affect. If none of the boxes relate to
your changes, release notes aren't required.

For each box you select, include information after the relevant heading
that describes the impact of your changes that a user might notice and
any actions they must take to implement updates.

- [ ] Protocol: 
- [ ] Nodes (Validators and Full nodes): 
- [ ] gRPC:
- [ ] JSON-RPC: 
- [ ] GraphQL: 
- [ ] CLI: 
- [ ] Rust SDK:
- [ ] Indexing Framework: