refactor(catalog): the HTTP layer reads through queries and writes through the service

Channels, search and sync do no database work in their routes any more: reads go through
catalog/queries, writes through catalog/service, and a live search's ingest is catalog/search.
What a catalog route needs from Reader (a playlist's channels, a user's tag links, the feed
projection of results) it asks reader/queries and reader/service. The scheduler and the runs page
read channel titles and the work queue through catalog/queries. Catalog is fenced below its HTTP
layer: its owner filters go through userscope, it reads no other unit's tables, and its ingest
jobs commit only where they are named.

backend/app/routes/runs.py

@@ -19,7 +19,7 @@ from app import scheduler
 from app.auth import admin_user
 from app.db import get_db
 from app.models import JobRun, LogEvent, User
-from app.catalog.models import Channel
+from app.catalog import queries as catalog_queries
 from app.routes import _account as account
 from app.routes._keyset import PAGE_MAX, accounts, older_than, page, utc
 from app.runstatus import RunStatus
@@ -117,10 +117,7 @@ def list_runs(
         lambda r: r.started_at,
     )
     channels = {r.target for r in runs if r.job in scheduler.AD_HOC_JOBS and r.target}
-    titles: dict[str, str] = {}
-    if channels:
-        rows = db.execute(select(Channel.id, Channel.title).where(Channel.id.in_(channels)))
-        titles = {cid: title for cid, title in rows.tuples() if title is not None}
+    titles = catalog_queries.channel_titles(db, channels)
     lines: dict[int, int] = {}
     if runs:
         counted = db.execute(