feat(tracks): filter track list by ingest source

Add an optional `source` filter to `GET /api/v1/tracks` (and the
`TrackRepository.list`/`count` port + SQLAlchemy adapter). Lets clients
query, e.g., only uploaded tracks (`?source=upload`) newest-first — the
backing for the webui's persistent "Recently uploaded" view.

- test: upload then list with `?source=upload` (hit) / `?source=youtube`
  (miss)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/infrastructure/db/repositories/track_repository.py

@@ -170,6 +170,7 @@ class SqlAlchemyTrackRepository:
         artist_id: uuid.UUID | None,
         album_id: uuid.UUID | None,
         q: str | None,
+        source: str | None = None,
         sort_by: str = "created_at",
         order: str = "desc",
         limit: int = 50,
@@ -180,6 +181,8 @@ class SqlAlchemyTrackRepository:
             stmt = stmt.where(TrackModel.artist_id == artist_id)
         if album_id is not None:
             stmt = stmt.where(TrackModel.album_id == album_id)
+        if source is not None:
+            stmt = stmt.where(TrackModel.source == source)
         if q:
             stmt = stmt.where(TrackModel.title.ilike(f"%{q}%"))
 
@@ -204,12 +207,15 @@ class SqlAlchemyTrackRepository:
         artist_id: uuid.UUID | None,
         album_id: uuid.UUID | None,
         q: str | None,
+        source: str | None = None,
     ) -> int:
         stmt = select(func.count()).select_from(TrackModel)
         if artist_id is not None:
             stmt = stmt.where(TrackModel.artist_id == artist_id)
         if album_id is not None:
             stmt = stmt.where(TrackModel.album_id == album_id)
+        if source is not None:
+            stmt = stmt.where(TrackModel.source == source)
         if q:
             stmt = stmt.where(TrackModel.title.ilike(f"%{q}%"))
         return (await self._session.execute(stmt)).scalar_one()