A fixed debounce can't fit a big library — 8500 movies + 4500 shows scan sequentially
through Plex's queue and can take 10-20 min, so the old 120s wait read the DB before
Plex finished and fresh downloads showed up late. Now Stage 1 (video_scan_server)
fires the rescan then POLLS the server until its scan queue goes idle, then emits the
done event.
- sources: PlexVideoSource.is_scanning (section.refreshing + activity feed, scoped by
media_type) and JellyfinVideoSource.is_scanning (scheduled-task state), plus
video_server_scan_in_progress() returning True/False/None.
- handler: pure wait_for_server_scan(scan_status, sleep, …) — grace, then poll every
interval until idle or a generous cap; falls back to the fixed wait only when the
server can't report status (None). debounce_seconds is now that fallback; new
max_wait_minutes caps the poll.
Seam tests for the poll logic (idle/poll/fallback/cap/lost-status), the handler wiring,
and Plex scan-status detection.
a16afd1f9e