Add trending movies/series, refreshed on a schedule

Mirrors TMDb's own /trending/{movie|tv}/{day|week} ranking rather than
Aurora computing trending itself from popularity deltas -- that would
require re-syncing the entire catalog on a schedule, infeasible at any
real scale, whereas TMDb already computes this well from signals (real
view/search velocity) Aurora has no access to.

New: TrendingEntry model + migration 0003, MetadataProvider.get_trending
(concrete/optional, like aclose(), so existing test fakes don't all need
updating), refresh_trending() which actually ingests each trending item
(only ~20 per window, cheap enough to fully ingest rather than apply the
never-fabricate-a-stub rule recommendations uses), a twice-daily arq cron
job (WorkerSettings.cron_jobs, new to this codebase), a manual admin
trigger for right after a deploy, and GET /movies/trending + GET
/series/trending.

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

app/models/__init__.py

@@ -24,6 +24,7 @@ from app.models.movie import (
 )
 from app.models.person import Person
 from app.models.provider import IngestionJob, Provider, ProviderRecord
+from app.models.trending import TrendingEntry
 from app.models.tv import (
     Episode,
     Season,
@@ -75,4 +76,5 @@ __all__ = [
     "Video",
     "WatchProvider",
     "WatchProviderOffering",
+    "TrendingEntry",
 ]