bug: the wishlist badge read /wishlist/counts 'total', which was movies+episodes
only — YouTube videos (kind='video') are counted by a separate method and were
left out. so a wishlist of only youtube videos showed NO number; it only lit up
once tv episodes were added.
fix: the /wishlist/counts endpoint now folds youtube_wishlist_counts().video into
the total (+ exposes video/channel counts). the badge already live-refreshes on
wishlist-changed events (which youtube add/remove fire), so it now updates for
youtube too. db methods unchanged (their byte-identical contract is intact).
regression tests: mixed + youtube-only.
The wishlist page had no way to empty a tab — only per-item remove. Added a red-tinted
'Clear all' button in the toolbar that empties the ACTIVE tab in one click (after a
confirm), shown only when that tab has items.
- db.clear_wishlist(kind) maps the tab to its rows (movie→'movie', show→'episode',
youtube→'video') and deletes them; returns the count.
- POST /api/video/wishlist/clear {kind: movie|show|youtube}.
- Toolbar button + clearAll() (confirm → clear → reload) + updateClearBtn() visibility.
Tests: per-tab clear leaves the others intact, unknown-kind/empty no-ops, the endpoint,
and the frontend wiring. node --check clean.
