Phase 2 scaffold: mitra online status & pairing logic

Add mitra online/offline status with heartbeat-based auto-offline,
customer-mitra pairing via Valkey pub/sub blast, session management,
and control center dashboard with real-time stats.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/src/db/migrate.js

@@ -64,6 +64,84 @@ const migrate = async () => {
     ON CONFLICT (key) DO NOTHING
   `
 
+  // --- Phase 2: Mitra Online Status & Pairing ---
+
+  await sql`
+    CREATE TABLE IF NOT EXISTS mitra_online_status (
+      id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+      mitra_id UUID NOT NULL UNIQUE REFERENCES mitras(id),
+      is_online BOOLEAN NOT NULL DEFAULT FALSE,
+      last_online_at TIMESTAMPTZ,
+      last_offline_at TIMESTAMPTZ,
+      last_heartbeat_at TIMESTAMPTZ,
+      updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+    )
+  `
+
+  await sql`
+    CREATE TABLE IF NOT EXISTS mitra_online_logs (
+      id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+      mitra_id UUID NOT NULL REFERENCES mitras(id),
+      status VARCHAR(10) NOT NULL,
+      timestamp TIMESTAMPTZ NOT NULL DEFAULT NOW()
+    )
+  `
+
+  await sql`
+    CREATE INDEX IF NOT EXISTS idx_mitra_online_logs_mitra_id
+    ON mitra_online_logs (mitra_id)
+  `
+
+  await sql`
+    CREATE TABLE IF NOT EXISTS chat_sessions (
+      id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+      customer_id UUID NOT NULL REFERENCES customers(id),
+      mitra_id UUID REFERENCES mitras(id),
+      status VARCHAR(30) NOT NULL DEFAULT 'searching',
+      created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+      paired_at TIMESTAMPTZ,
+      ended_at TIMESTAMPTZ,
+      ended_by VARCHAR(20)
+    )
+  `
+
+  await sql`
+    CREATE INDEX IF NOT EXISTS idx_chat_sessions_customer_id
+    ON chat_sessions (customer_id)
+  `
+
+  await sql`
+    CREATE INDEX IF NOT EXISTS idx_chat_sessions_mitra_id
+    ON chat_sessions (mitra_id)
+  `
+
+  await sql`
+    CREATE INDEX IF NOT EXISTS idx_chat_sessions_status
+    ON chat_sessions (status)
+  `
+
+  await sql`
+    CREATE TABLE IF NOT EXISTS chat_request_notifications (
+      id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+      session_id UUID NOT NULL REFERENCES chat_sessions(id),
+      mitra_id UUID NOT NULL REFERENCES mitras(id),
+      notified_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+      response VARCHAR(20),
+      responded_at TIMESTAMPTZ
+    )
+  `
+
+  await sql`
+    CREATE INDEX IF NOT EXISTS idx_chat_request_notifications_session_id
+    ON chat_request_notifications (session_id)
+  `
+
+  await sql`
+    INSERT INTO app_config (key, value)
+    VALUES ('max_customers_per_mitra', '{"value": 3}')
+    ON CONFLICT (key) DO NOTHING
+  `
+
   console.log('Migration complete.')
   await sql.end()
 }