- support ping incoming event and pong outgoing response
- add web heartbeat interval to keep ws alive
- add stale-connection watchdog to force reconnect on missing pong
- add websocket events user_online/user_offline
- broadcast presence changes on first connect and final disconnect only
- apply live presence updates in web chat store and realtime hook
- move public discover into unified left search (users + groups/channels)
- remove separate Discover Chats dialog/menu entry
- add reply_to/forwarded_from message fields and chat pinned_message field
- add forward and pin APIs plus reply support in message create
- wire web actions: Reply, Fwd, Pin and reply composer state
- fix spam policy bug: allow repeated identical messages, keep rate limiting