Fix feed contamination, notification persistence, relay reconnection, and wallet reliability

[barrydeen]

Summary

• Fix feed contamination: Events from user profile, thread, and bookmark subscriptions were being added to the follow feed via addEvent() in the catch-all else block of processRelayEvent. This caused posts from non-followed users to appear in the feed after viewing their profiles, and inflated the "new posts" counter (the count included every post loaded on profile screens). Now only feed-related subscriptions (feed, loadmore, feed-backfill) call addEvent() — everything else uses cacheEvent() which stores events for lookups without inserting into the feed list.

• Fix UserProfileViewModel feed leakage: The profile screen was also calling eventRepo.addEvent() for kind 0/1/6 events, which inserted viewed users' posts into the global feed. Changed to cacheEvent() since the profile screen maintains its own local lists. Also chunked follow-profile requests into batches of 50 with proper subscription cleanup.

• Persist notification read state: Unread notification badge now survives app restarts by persisting the last-read timestamp in SharedPreferences (per account). Notifications are only marked unread if they're newer than the stored timestamp.

• Fix relay reconnection: WebSocket onClosed with non-normal close codes (anything other than 1000) now triggers reconnection. The socket reference is also nulled on close to prevent sends to dead connections.

• Improve wallet connection reliability: Rewrote the NWC connection flow — initial connect uses a proper coroutine timeout, then a persistent monitor handles disconnect/reconnect state transitions. The NWC relay now receives a coroutine scope for proper lifecycle management. Removed initNwc() since wallet connects lazily when the tab is opened or on-demand when sending a zap.

Test plan

• Pull to refresh the feed — verify the "new posts" counter starts at 0 and only counts genuinely new streaming events
• Visit a non-followed user's profile, navigate back to feed — verify their posts don't appear in the follow feed
• View notifications, restart app — verify unread badge reflects actual unread state
• Disconnect from network briefly, reconnect — verify relays reconnect and feed resumes
• Connect NWC wallet, navigate away and back — verify wallet stays connected and shows balance
• Send a zap without visiting the wallet tab first — verify NWC connects on demand