Add deprecation, sunset, and successor headers to FastAPI routes

Normalized profile

What this task asks for

Add runtime Deprecation, Sunset, and Link headers plus OpenAPI metadata and tracking middleware for deprecated routes. FastAPI currently treats `deprecated=True` as schema metadata only (`"deprecated": true`) and does not add runtime response signals. Any route with `deprecated=True` must emit `Deprecation: true`. Add `sunset: datetime | None`. Add `deprecation_date: datetime | None`. Add `successor_url: str | None`. The existing `deprecated` parameter must also follow the same propagation and inheritance rules described below (it already exists on routes, routers, and `include_router` calls; ensure it propagates consistently with the new parameters).