3afe96a8cd
New ytsage/utils/ytsage_library_manager.py: sagetube_library.db (separate from the upstream download-history DB) with WAL from day one, holding subscriptions, cached feed_items, watch_history with resume positions, and the persisted play_queue. Watch history and queue tables are wired up by the next commit. FeedPage: - Local mode: FeedRefreshWorker refreshes each subscribed channel sequentially (feed.per_channel_items, default 15) and the grid fills incrementally per channel; results are cached so the feed is populated instantly on startup. - Account mode: fetches youtube.com/feed/subscriptions with the user's browser cookies - the real logged-in feed; the option is enabled only while cookies are active and errors surface as a status banner. - Sidebar lists subscriptions (double-click opens the channel in Browse; context menu unsubscribes). Browse's Subscribe button now toggles subscription state through the Feed page. Verified live: subscribe -> refresh -> 15 videos cached in SQLite and rendered as cards. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>