Add GET /genres directory endpoint

GET /movies and GET /series accept a genre filter (an Aurora genre id),
but nothing exposed what those ids actually are -- genres otherwise
only ever appear embedded in a movie/series response's own genres
list. This is the resolve-by-name-first-then-filter step the frontend
needs to build real genre browsing.

No filter, no sort_by -- always alphabetical by name, same pattern as
collections/companies (genres have no categorical field or popularity/
date to sort by). page_size defaults to 50 (max 200) rather than the
20/50 used elsewhere, since genres are a small, fixed reference set
(TMDb has ~19-20 total) a client typically wants in full for a filter
dropdown, not paginated like a catalog of millions of movies.

Also fixed two stale "behind Traefik" mentions in app/main.py's module
docstring while touching this file, left over from the earlier
cPanel/host-webserver deployment change.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

app/api/v1/genres.py

@@ -0,0 +1,28 @@
+"""Genre endpoints (section 17: additive) -- a directory for the `genre`
+filter GET /movies and GET /series already accept, which takes an Aurora
+genre id with no prior way to discover what those ids are."""
+
+from __future__ import annotations
+
+from fastapi import APIRouter, Depends, Query
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.core.database import get_db
+from app.core.security import enforce_rate_limit
+from app.schemas.common import GenreListOut
+from app.services import genre_service
+
+router = APIRouter(prefix="/genres", tags=["genres"], dependencies=[Depends(enforce_rate_limit)])
+
+
+@router.get("", response_model=GenreListOut)
+async def list_genres(
+    page: int = Query(1, ge=1),
+    # Genres are a small, fixed reference set (TMDb has ~19-20 total) --
+    # default/max page_size sized so a client can fetch the whole
+    # directory in one call for a filter dropdown, unlike the huge
+    # catalogs GET /movies etc. paginate through.
+    page_size: int = Query(50, ge=1, le=200),
+    session: AsyncSession = Depends(get_db),
+) -> GenreListOut:
+    return await genre_service.list_genres(session, page=page, page_size=page_size)