Fix two more test bugs surfaced by the full integration run

1. test_ingestion_cache_invalidation.py: the job was created through
   the test's db_session fixture, whose commit() only ends a savepoint
   that gets rolled back at teardown (see tests/conftest.py) -- it's
   never a real commit. _run_ingestion looks the job up through its
   own session_scope() (a genuinely separate connection), which could
   never see it, so the very first _require_job call raised "job
   vanished mid-run" every time. Worse, test_failed_ingestion_does_not_
   invalidate_the_cache still passed, coincidentally -- it expected a
   RuntimeError and got one, just the wrong one, masking the bug.
   Fixed by having _make_job create the job through session_scope()
   itself, matching test_ingestion_retry.py's existing pattern.

2. Same class of bug as the video-collision fix in the last commit:
   FAKE_MOVIE's fixed imdb_id ("tt0133093"), not just its video, also
   collides across two different fake movies sharing it unmodified --
   uq_external_id_source is a real unique constraint on
   (provider_id, entity_type, external_id). Fixed by also overriding
   imdb_id on the second movie in both affected tests.

All caught by running the actual integration suite against Postgres --
these paths were previously only collect-only'd locally (no local DB).

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

tests/integration/test_collection_ingestion.py

@@ -57,9 +57,10 @@ async def test_ingest_collection_only_links_already_ingested_movies(db_session:
     already knows about, in release-date order, never fabricate a stub for
     the other two (section 15)."""
 
-    # 604's videos overridden to empty: FAKE_MOVIE's embedded video has a
-    # fixed provider_video_id, and two different movies both ingesting it
-    # would collide on the real uq_video_provider_source unique constraint.
+    # 604's videos and imdb_id overridden: FAKE_MOVIE's embedded video and
+    # imdb_id are both fixed identifiers, and two different movies both
+    # ingesting them unmodified would collide on the real
+    # uq_video_provider_source / uq_external_id_source unique constraints.
     provider = FakeTMDbCollectionProvider(
         movie_payloads={
             "603": {**FAKE_MOVIE, "id": 603, "title": "The Matrix"},
@@ -68,6 +69,7 @@ async def test_ingest_collection_only_links_already_ingested_movies(db_session:
                 "id": 604,
                 "title": "The Matrix Reloaded",
                 "videos": {"results": []},
+                "imdb_id": "tt0234215",
             },
         },
         collection_payload=FAKE_COLLECTION,