feat(sync): phase 1 - import Takeout + Watch Later YouTube bidirectionnel
- Takeout: POST /user/history/takeout (lots <=1000, validation videoId,
upsert sans doublons), parsing local watch-history.json cote client
(vie privee, dedup derniere date), progression par lots de 500
- Watch Later: GET/POST /oauth/google/watchlater (lecture readonly,
push force-ssl), import vers playlist NewTube 'Watch Later (YouTube)',
export playlist NewTube -> WL YouTube, writeGranted + invite reconnect
- Scopes Google elargis (youtube.force-ssl), aide /library/import a jour
(limite historique API documentee)