MVP: IRC envelope format, long-polling, per-client queues, SPA rewrite

Major changes:
- Consolidated schema into single migration with IRC envelope format
- Messages table stores command/from/to/body(JSON)/meta(JSON) per spec
- Per-client delivery queues (client_queues table) with fan-out
- In-memory broker for long-poll notifications (no busy polling)
- GET /messages supports ?after=<queue_id>&timeout=15 long-polling
- All commands (JOIN/PART/NICK/TOPIC/QUIT/PING) broadcast events
- Channels are ephemeral (deleted when last member leaves)
- PRIVMSG to nicks (DMs) fan out to both sender and recipient
- SPA rewritten in vanilla JS (no build step needed):
  - Long-poll via recursive fetch (not setInterval)
  - IRC envelope parsing with system message display
  - /nick, /join, /part, /msg, /quit commands
  - Unread indicators on inactive tabs
  - DM tabs from user list clicks
- Removed unused models package (was for UUID-based schema)
- Removed conflicting UUID-based db methods
- Increased HTTP write timeout to 60s for long-poll support

internal/db/schema/001_initial.sql

@@ -1,4 +1,54 @@
-CREATE TABLE IF NOT EXISTS schema_migrations (
-    version INTEGER PRIMARY KEY,
-    applied_at DATETIME DEFAULT CURRENT_TIMESTAMP
+-- Chat server schema (pre-1.0 consolidated)
+PRAGMA foreign_keys = ON;
+
+-- Users: IRC-style sessions (no passwords, just nick + token)
+CREATE TABLE IF NOT EXISTS users (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    nick TEXT NOT NULL UNIQUE,
+    token TEXT NOT NULL UNIQUE,
+    created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+    last_seen DATETIME DEFAULT CURRENT_TIMESTAMP
 );
+CREATE INDEX IF NOT EXISTS idx_users_token ON users(token);
+
+-- Channels
+CREATE TABLE IF NOT EXISTS channels (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    name TEXT NOT NULL UNIQUE,
+    topic TEXT NOT NULL DEFAULT '',
+    created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+    updated_at DATETIME DEFAULT CURRENT_TIMESTAMP
+);
+
+-- Channel members
+CREATE TABLE IF NOT EXISTS channel_members (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    channel_id INTEGER NOT NULL REFERENCES channels(id) ON DELETE CASCADE,
+    user_id INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    joined_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+    UNIQUE(channel_id, user_id)
+);
+
+-- Messages: IRC envelope format
+CREATE TABLE IF NOT EXISTS messages (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    uuid TEXT NOT NULL UNIQUE,
+    command TEXT NOT NULL DEFAULT 'PRIVMSG',
+    msg_from TEXT NOT NULL DEFAULT '',
+    msg_to TEXT NOT NULL DEFAULT '',
+    body TEXT NOT NULL DEFAULT '[]',
+    meta TEXT NOT NULL DEFAULT '{}',
+    created_at DATETIME DEFAULT CURRENT_TIMESTAMP
+);
+CREATE INDEX IF NOT EXISTS idx_messages_to_id ON messages(msg_to, id);
+CREATE INDEX IF NOT EXISTS idx_messages_created ON messages(created_at);
+
+-- Per-client message queues for fan-out delivery
+CREATE TABLE IF NOT EXISTS client_queues (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    user_id INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    message_id INTEGER NOT NULL REFERENCES messages(id) ON DELETE CASCADE,
+    created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+    UNIQUE(user_id, message_id)
+);
+CREATE INDEX IF NOT EXISTS idx_client_queues_user ON client_queues(user_id, id);