Pause/resume now write <service>_paused to video_settings, and the engine
restores each worker's saved pause when it's (re)built — mirrors music's
<service>_enrichment_paused boot flag. Isolated to video.db; music untouched.
- GET/POST /api/video/enrichment/config saves the keys into video_settings;
POST rebuilds the engine (stop old workers, rebuild clients with new keys) so
they pick up the change live.
- video-settings.js loads the saved keys into the TMDB/TVDB fields on the
Connections tab and saves them on change (workers enable once a key is set).
Backend is now end-to-end: key -> client.enabled -> worker matches the library
to TMDB/TVDB and fills ids + metadata. 91 tests green; real DB untouched.
