Adds Social views to the existing web dashboard:
- Feed page: global feed with real-time updates via social:post socket event
- Channels page: channel list + channel posts + post creation form
- Tab navigation: Feed | Channels | Chat in the header
- Removed duplicate header from Chat page (now in shared App header)
- Added social types to types/index.ts and API methods to lib/api.ts
- Added social:post event type to socket client
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
