Backend:
- Session/client UUID model: sessions table (uuid, nick, signing_key),
clients table (uuid, session_id, token) with per-client message queues
- MOTD delivery as IRC numeric messages (375/372/376) on connect
- EnqueueToSession fans out to all clients of a session
- EnqueueToClient for targeted delivery (MOTD)
- All queries updated for session/client model
SPA client:
- Long-poll loop (15s timeout) instead of setInterval
- IRC message envelope parsing (command/from/to/body)
- Display JOIN/PART/NICK/TOPIC/QUIT system messages
- Nick change via /nick command
- Topic display in header bar
- Unread count badges on inactive tabs
- Auto-rejoin channels on reconnect (localStorage)
- Connection status indicator
- Message deduplication by UUID
- Channel history loaded on join
- /topic command support
Closes#9
