Round-1 review finding #4 named only audit.py/plex.py, but the same misplaced
`from app.utils import iso` sat in channels/downloads/feed/notifications too — the
round missed them (ruff enforces no import order here, so the gate was silent).
Move them to alphabetical position for consistency. No behaviour change.
Establish the R6 API-contract infra before the S1b payload:dict migration:
- iso(dt) in utils.py replaces the ~16 hand-rolled `x.isoformat() if x else None`
serializer idioms across the routes.
- get_or_404 / owned_or_404 in routes/_common.py — one 404 + existence-leak policy;
plex's _own_playlist_or_404 and saved_views' _own_view now delegate to it.
- require_write_scope dependency in auth.py collapses the inline has_write_scope→403
checks (channels subscribe/unsubscribe, playlists push/push-plan) that had drifted
into three different messages into one; the conditional delete_playlist guard stays
inline (its message was already canonical).
No response-shape change (iso == isoformat for a present value). Gate: ruff clean,
pytest 163 green (+ test_utils for iso).
Add a server-backed notification center that coexists with the client-side
transient bell: a per-user `notifications` table (type/title/body/data JSON/
read/dismissed), a `/api/me/notifications` CRUD API (list, unread_count, read,
read_all, dismiss, clear), and a left-nav inbox module with a live unread badge
polled via useLiveQuery. Known types render trilingual text from type+data
(English stored text is the fallback); read rows are trimmed past a soft cap.
Also adds the schema the maintenance job builds on: videos.list?part=status
columns (embeddable/privacy_status/upload_status) and the validation lifecycle
columns (last_checked_at, unavailable_since, unavailable_reason).
Page-id validation is centralized in one PAGES source of truth (isPage) so the
new page survives reload without a second allowlist to keep in sync.
peter