Adopt FastAPI Annotated[] DI pattern across API layer

[pavelzbornik]

Problem

The API layer uses the legacy param: Type = Depends() pattern for dependency injection. SonarCloud flags 52 blocker-level code smells for this across the API layer.

The modern FastAPI pattern (since v0.95+) uses Annotated:

# Old pattern
async def endpoint(service: MyService = Depends()):

# New pattern
from typing import Annotated
async def endpoint(service: Annotated[MyService, Depends()]):

Affected Files

• app/api/audio_api.py — 12 instances
• app/api/audio_services_api.py — 20 instances
• app/api/task_api.py — 3 instances
• app/api/dependencies.py — dependency provider definitions

Tasks

• Define reusable type aliases in app/api/dependencies.py (e.g., AudioService = Annotated[AudioService, Depends(get_audio_service)])
• Update audio_api.py endpoints to use Annotated[]
• Update audio_services_api.py endpoints to use Annotated[]
• Update task_api.py endpoints to use Annotated[]
• Run task check && task test to verify no regressions

Acceptance Criteria

• All Depends() calls in API endpoints use Annotated[] pattern
• SonarCloud blocker code smells resolved
• All tests pass, coverage maintained >=80%