Deep-review round 5, over round 4's own fixes.
- `notifyActionError` preferred the server's `detail` over the caller's translated fallback, and
`reportFailure` deliberately leaves 403/404/429 to the caller — so for exactly those statuses the
dozen call sites round 4 converted started printing whatever English a route hand-wrote into an
otherwise Hungarian UI ("No user with that email.", "Not subscribed to this channel", "Unknown
job"). A STRUCTURED detail is still preferred: `req` has already run it through `localizeDetail`,
so it is both localized and more specific. A plain string is not.
- The other half of the same defect, on the backend: round 4's `get_or_404(what="channel")` sweep
reached exactly ONE of the five identical sites in channels.py and shipped the HU/EN string with
it, so the Block button said it in Hungarian and the four controls beside it in English. All five
are converted, and the subscription / share-recipient / scheduler-job 404s with them (two new
reasons in both locales).
- `PlexCollectionEditor`'s add/remove, take-over and delete were try/finally with no catch — in the
very file round 4 edited to give `createNew` one. 403 and 404 are the caller's to report, so the
tick simply never appeared and a CONFIRMED "delete collection" did nothing, silently.
- `UploadDialog` is the only `uploadReq` caller and kept an empty catch whose comment still claimed
the global error modal had it. It had not since `reportFailure` became shared: a proxy 502 raised
only the self-clearing connection notice and a 413/403/404 nothing at all, so the dialog snapped
back to its pre-upload state with no error named. The user's own Cancel stays silent — and since
a cancel and a network drop both carry status 0, that difference is now a named `isAborted`
rather than a string literal at each end.
Regression tests for each (5 vitest, 2 pytest, plus two existing assertions corrected), all
mutation-checked: 6 mutations, each red on the assertion it is named after. vitest 1007,
pytest 1127.