api/video/youtube.py wired into the blueprint:
- GET /youtube/resolve — preview a pasted channel (meta + recent uploads) +
a 'following' hydration flag; no writes.
- POST /youtube/follow — {url} or pre-resolved {channel} → follow + wish its
recent uploads (capped 30). Returns channel + counts.
- POST /youtube/unfollow — {youtube_id} → un-follow (keeps wished videos).
- GET /youtube/channels — followed channels for the watchlist page.
- GET /youtube/wishlist — wished videos grouped by channel.
- POST /youtube/wishlist/remove — scope channel|video.
yt-dlp call lives behind resolve (injectable/mockable). 38 API tests green.
