Phase 3 scaffold: chat engine (WebSocket, FCM, pricing, timer, extension, history)

- Backend: WebSocket plugin, chat/pricing/timer/extension/closure/notification services
- Client app: ChatBloc, pricing dialog, chat screen with message status, extension/goodbye flow, history
- Mitra app: MitraChatBloc, ExtensionBloc, chat screen, extension accept/reject, history
- Control center: free trial, extension timeout, early end config toggles
- DB migration: chat_messages, session_closures, session_extensions, customer_transactions tables

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

backend/src/db/migrate.js

@@ -142,6 +142,125 @@ const migrate = async () => {
     ON CONFLICT (key) DO NOTHING
   `
 
+  // --- Phase 3: Chat Engine ---
+
+  // Add session duration/pricing columns to chat_sessions
+  await sql`
+    ALTER TABLE chat_sessions
+    ADD COLUMN IF NOT EXISTS duration_minutes INT,
+    ADD COLUMN IF NOT EXISTS price INT DEFAULT 0,
+    ADD COLUMN IF NOT EXISTS is_free_trial BOOLEAN NOT NULL DEFAULT FALSE,
+    ADD COLUMN IF NOT EXISTS expires_at TIMESTAMPTZ,
+    ADD COLUMN IF NOT EXISTS extended_minutes INT NOT NULL DEFAULT 0
+  `
+
+  // Add FCM token columns
+  await sql`
+    ALTER TABLE customers
+    ADD COLUMN IF NOT EXISTS fcm_token VARCHAR(255)
+  `
+
+  await sql`
+    ALTER TABLE mitras
+    ADD COLUMN IF NOT EXISTS fcm_token VARCHAR(255)
+  `
+
+  await sql`
+    CREATE TABLE IF NOT EXISTS chat_messages (
+      id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+      session_id UUID NOT NULL REFERENCES chat_sessions(id),
+      sender_type VARCHAR(10) NOT NULL,
+      sender_id UUID NOT NULL,
+      type VARCHAR(20) NOT NULL DEFAULT 'text',
+      content TEXT NOT NULL,
+      metadata JSONB,
+      status VARCHAR(20) NOT NULL DEFAULT 'sent',
+      delivered_at TIMESTAMPTZ,
+      read_at TIMESTAMPTZ,
+      created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+    )
+  `
+
+  await sql`
+    CREATE INDEX IF NOT EXISTS idx_chat_messages_session_created
+    ON chat_messages (session_id, created_at)
+  `
+
+  await sql`
+    CREATE INDEX IF NOT EXISTS idx_chat_messages_session_status
+    ON chat_messages (session_id, status)
+  `
+
+  await sql`
+    CREATE TABLE IF NOT EXISTS session_closures (
+      id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+      session_id UUID NOT NULL REFERENCES chat_sessions(id),
+      user_type VARCHAR(10) NOT NULL,
+      user_id UUID NOT NULL,
+      message TEXT NOT NULL,
+      created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+    )
+  `
+
+  await sql`
+    CREATE TABLE IF NOT EXISTS session_extensions (
+      id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+      session_id UUID NOT NULL REFERENCES chat_sessions(id),
+      requested_duration_minutes INT NOT NULL,
+      requested_price INT NOT NULL,
+      status VARCHAR(20) NOT NULL DEFAULT 'pending',
+      requested_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+      responded_at TIMESTAMPTZ
+    )
+  `
+
+  await sql`
+    CREATE TABLE IF NOT EXISTS customer_transactions (
+      id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+      customer_id UUID NOT NULL REFERENCES customers(id),
+      session_id UUID NOT NULL REFERENCES chat_sessions(id),
+      type VARCHAR(20) NOT NULL,
+      amount INT NOT NULL DEFAULT 0,
+      created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+    )
+  `
+
+  await sql`
+    CREATE INDEX IF NOT EXISTS idx_customer_transactions_customer_id
+    ON customer_transactions (customer_id)
+  `
+
+  // Phase 3 config keys
+  await sql`
+    INSERT INTO app_config (key, value)
+    VALUES ('free_trial_enabled', '{"value": true}')
+    ON CONFLICT (key) DO NOTHING
+  `
+
+  await sql`
+    INSERT INTO app_config (key, value)
+    VALUES ('free_trial_duration_minutes', '{"value": 5}')
+    ON CONFLICT (key) DO NOTHING
+  `
+
+  await sql`
+    INSERT INTO app_config (key, value)
+    VALUES ('extension_timeout_seconds', '{"value": 60}')
+    ON CONFLICT (key) DO NOTHING
+  `
+
+  await sql`
+    INSERT INTO app_config (key, value)
+    VALUES ('early_end_mitra_enabled', '{"value": false}')
+    ON CONFLICT (key) DO NOTHING
+  `
+
+  await sql`
+    INSERT INTO app_config (key, value)
+    VALUES ('early_end_customer_enabled', '{"value": false}')
+    ON CONFLICT (key) DO NOTHING
+  `
+
   console.log('Migration complete.')
   await sql.end()
 }