/code-review high round 1 (5 findings):
- iso(dt) now typed `date | None` — MediaAsset.upload_date is a plain `date`, not a
datetime; the helper's signature was too narrow for the type-contract epic. +test.
- restore alphabetical app.* import order in audit.py and plex.py (the new iso/_common
imports had been dropped in mid-block).
The other 3 findings are deliberate design choices, left as-is for UAT: push/push-plan
now gate write-scope before the 404 (dependency ordering); the unified 403 message; and
owned_or_404's owner_attr kept for S1b's DownloadShare.to_user_id-style owners.
Gate: ruff clean, pytest 164 green.
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).
peter