Same "channels per category" counts as the categories management page,
now next to each button in the sidebar used across all three pages.
Categories already carry channel_count; "Все"/"Без категории" counts are
derived client-side from one extra unfiltered channels query, reused
across the three pages via a shared ['channels', 'all-for-counts'] key.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
- GET /api/channels called with subscribed=true from the Channels page, so
a channel disappears from the list as soon as it's unsubscribed instead
of lingering with a badge
- GET /api/feed gains a `downloaded` filter (this was already anticipated
in the original TZ's feed query params but left unimplemented until
download_jobs existed) -- matches on each video's *latest* job only, so
a redownload/delete history doesn't leave stale matches
- New /saved route: same category filtering, video grid and download
actions as the main feed, scoped to downloaded videos only
2 new backend tests (76 total).
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
