chore(scheduler): dedup token-user query + drop pointless rss lambda

- Extract runner.token_users(db): the "all users with a stored refresh token"
  query was spelled 3× (get_service_user, run_subscription_resync,
  sync_all_playlists). get_service_user now reuses it ([0]); sync_all_playlists
  imports it from runner (no cycle — runner doesn't import playlists); the now-
  unused OAuthToken import is dropped there.
- scheduler.py: _job("rss_poll", lambda db: run_rss_poll(db)) → _job("rss_poll",
  run_rss_poll) — the lambda was dead indirection; all sibling jobs pass the
  callable directly and _job calls fn(db).

Behavior-neutral. ruff clean, localdev boots, re-review clean.

backend/app/scheduler.py

@@ -209,7 +209,7 @@ def scheduler_snapshot() -> dict:
 
 
 def _rss_job() -> None:
-    _job("rss_poll", lambda db: run_rss_poll(db))
+    _job("rss_poll", run_rss_poll)
 
 
 def _enrich_job() -> None:

backend/app/sync/playlists.py

@@ -14,7 +14,8 @@ from sqlalchemy.orm import Session
 
 from app import progress, quota
 from app.auth import has_read_scope
-from app.models import Channel, OAuthToken, Playlist, PlaylistItem, User, Video
+from app.models import Channel, Playlist, PlaylistItem, User, Video
+from app.sync.runner import token_users
 from app.sync.videos import apply_video_details, parse_dt
 from app.youtube.client import YouTubeClient, YouTubeError
 
@@ -370,13 +371,7 @@ def repull_playlist(db: Session, user: User, pl: Playlist) -> dict:
 
 def sync_all_playlists(db: Session) -> dict:
     """Scheduler entry point: mirror playlists for every user with a read scope + token."""
-    users = (
-        db.execute(
-            select(User).join(OAuthToken).where(OAuthToken.refresh_token_enc.is_not(None))
-        )
-        .scalars()
-        .all()
-    )
+    users = token_users(db)
     total = 0
     for i, user in enumerate(users, 1):
         if not has_read_scope(user):

backend/app/sync/runner.py

@@ -31,17 +31,21 @@ from app.youtube.rss import fetch_channel_feed
 RSS_POLL_WORKERS = 16
 
 
-def get_service_user(db: Session) -> User | None:
-    return (
+def token_users(db: Session) -> list[User]:
+    """Every user with a stored YouTube refresh token (the read-scope service accounts), by id."""
+    return list(
         db.execute(
             select(User)
             .join(OAuthToken)
             .where(OAuthToken.refresh_token_enc.is_not(None))
             .order_by(User.id)
+        ).scalars()
     )
-        .scalars()
-        .first()
-    )
+
+
+def get_service_user(db: Session) -> User | None:
+    users = token_users(db)
+    return users[0] if users else None
 
 
 def run_rss_poll(db: Session, channels: list[Channel] | None = None) -> int:
@@ -102,15 +106,7 @@ def run_shorts(db: Session) -> dict:
 def run_subscription_resync(db: Session) -> dict:
     """Re-import every user's subscriptions so unsubscribes and new subscriptions on
     YouTube are reflected automatically."""
-    users = (
-        db.execute(
-            select(User)
-            .join(OAuthToken)
-            .where(OAuthToken.refresh_token_enc.is_not(None))
-        )
-        .scalars()
-        .all()
-    )
+    users = token_users(db)
     for i, user in enumerate(users, 1):
         try:
             import_subscriptions(db, user)