Add series/season/episode ingestion pipeline

Movie and person ingestion existed, but the series/season/episode API
endpoints had no way to actually populate them from TMDb -- the
biggest remaining gap in Core 0.1's television scope.

- normalize_series/normalize_season in the metadata normalizer,
  including two TMDb quirks that would otherwise silently produce
  empty data: /tv nests keywords and alternative_titles under
  "results" (not "keywords"/"titles" like /movie), and series-level
  creators come from a separate created_by array, not the credits
  cast/crew lists.
- ingest_series upserts the Series row plus season *stubs* (number,
  title, air date, poster -- everything TMDb inlines on /tv/{id});
  ingest_season fetches and upserts one season's full episode list,
  and requires the series to already exist (TMDb has no single
  endpoint for a whole series' episodes, so this has to be a separate
  per-season call).
- Wired through the same job-lifecycle path as movie/person ingestion
  (runner.py, arq tasks, admin endpoints), with the shared boilerplate
  between them factored into runner._run_ingestion and
  admin.py:_enqueue rather than copy-pasted a third and fourth time.
- Unit tests for both normalizers (runnable without a DB) and
  integration tests for the full ingest_series -> ingest_season flow,
  including the series-must-exist-first error and idempotency on
  re-ingestion.

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

app/workers/worker.py

@@ -13,7 +13,12 @@ from arq.connections import RedisSettings
 
 from app.core.config import get_settings
 from app.core.logging import configure_logging, get_logger
-from app.workers.tasks import ingest_movie_task, ingest_person_task
+from app.workers.tasks import (
+    ingest_movie_task,
+    ingest_person_task,
+    ingest_season_task,
+    ingest_series_task,
+)
 
 logger = get_logger(__name__)
 
@@ -28,7 +33,7 @@ async def shutdown(ctx: dict) -> None:
 
 
 class WorkerSettings:
-    functions = [ingest_movie_task, ingest_person_task]
+    functions = [ingest_movie_task, ingest_person_task, ingest_series_task, ingest_season_task]
     on_startup = startup
     on_shutdown = shutdown
     redis_settings = RedisSettings.from_dsn(get_settings().REDIS_URL)