The browser Plex OAuth flow only sent the PMS server access token, which
the discover API rejects (401), so the watchlist step always failed with
a buried warning. The web client now forwards the plex.tv account token
via a new additive plex_account_token field.
The discover watchlist listing also ignores includeGuids, so items
arrived without external ids and could only exact-title/year match.
FetchWatchlist now resolves ids per item from the discover metadata
endpoint, decoding both Metadata- and Video-keyed containers, and
degrades to a title/year fallback warning instead of dropping items.
Part of #245
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
