Fix test isolation: trending tests were leaking data into other tests

Not a bug in production code -- refresh_trending()'s tests use
session_scope() for real, permanent commits (necessary, since
refresh_trending manages its own sessions), unlike every other
integration test's db_session fixture, which rolls back after each test.

FakeTrendingProvider reused FAKE_MOVIE/FAKE_SERIES unmodified except for
id/title, so every synthetic trending movie/series carried the same
embedded video id and imdb_id -- values meant to be globally unique per
real TMDb entity. Those commits were never rolled back, so they
permanently occupied uq_video_provider_source/uq_external_id_source in
the shared test database for the rest of the run, causing
test_watch_providers.py (which runs later alphabetically and ingests the
same fixtures unmodified via the normal rolled-back db_session) to
collide against leaked data with 14 failures that had nothing to do with
watch providers.

Found by actually running the full suite against real Postgres --
confirms it was worth doing before this deploys.

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

tests/integration/test_trending.py

@@ -36,10 +36,32 @@ class FakeTrendingProvider(MetadataProvider):
         self._series_ids = series_ids
 
     async def get_movie(self, external_id: str) -> dict[str, Any]:
-        return {**FAKE_MOVIE, "id": int(external_id), "title": f"Movie {external_id}"}
+        # FAKE_MOVIE's embedded video id and imdb_id are fixed identifiers
+        # meant to be globally unique per real TMDb movie -- reusing them
+        # unmodified across multiple synthetic movies here would collide
+        # on uq_video_provider_source / uq_external_id_source. Unlike
+        # every other test file (db_session rolls back per test),
+        # refresh_trending's session_scope() commits are never rolled
+        # back, so that collision would otherwise permanently poison the
+        # shared test database for every later test in the same run that
+        # also ingests FAKE_MOVIE unmodified (see test_watch_providers.py).
+        return {
+            **FAKE_MOVIE,
+            "id": int(external_id),
+            "title": f"Movie {external_id}",
+            "videos": {"results": []},
+            "imdb_id": None,
+            "external_ids": {},
+        }
 
     async def get_series(self, external_id: str) -> dict[str, Any]:
-        return {**FAKE_SERIES, "id": int(external_id), "name": f"Series {external_id}"}
+        # Same reasoning as get_movie above, for FAKE_SERIES's imdb_id/tvdb_id.
+        return {
+            **FAKE_SERIES,
+            "id": int(external_id),
+            "name": f"Series {external_id}",
+            "external_ids": {},
+        }
 
     async def get_season(self, series_external_id: str, season_number: int) -> dict[str, Any]:
         raise NotImplementedError