Phase 3.7: paid pairing flow + returning chat + extension flip

- Backend: payment_sessions + pairing_failures tables; payment.service.js
  and pairing-failure.service.js (new); rewritten pairing.service.js
  (payment-gated blast + targeted "Curhat lagi" + cancel + fallback);
  rewritten extension.service.js (data-driven auto-approve with offline
  safeguard, charge-at-approval); pricing.service.js (extension tiers
  without free trial); mitra-status.service.js (countAvailableMitras
  cached path); 60s sweeper for stale payment sessions
- Backend routes: client.payment.routes, client.mitra-availability.routes,
  internal/failed-pairings.routes; client.chat.routes rewritten for
  payment-gated start + /returning + /cancel + /fallback-to-blast;
  internal/config.routes adds 4 new keys with Valkey invalidate publish
- client_app: mitra-availability poll, payment screen + notifier, pairing
  notifier rewrite (PairingTargetedWaiting + PairingFailed states),
  targeted-waiting overlay + bestie-unavailable dialog, "Curhat lagi"
  CTA, failed-pairing terminal, extension via payment-session
- mitra_app: PairingRequestType enum, returning-chat 20s countdown
  auto-dismiss, extension card "otomatis disetujui" copy
- control_center: 4 new config rows in Settings, Failed Pairings page
  (filter + paginate + action menu), sidebar + route registered
- Test infrastructure: Vitest backend (7/7 pass), Playwright CC (4/4
  pass), Maestro mobile scaffold (CLI install pending)
- Bugs found via Playwright + fixed: LoginPage labels not associated
  with inputs (a11y); backend internal CORS missing PATCH/PUT/DELETE
  in allow-methods (silent settings breakage in browsers since Stage 4)
- Docs: phase3.7.md PRD, phase3.7-plan.md, phase3.7-questions.md (Q&A),
  phase3.7-testing.md (E2E checklist), phase3.7-test-run-2026-05-03.md
  (today's run results)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/test/helpers/db.js

@@ -0,0 +1,81 @@
+import { getDb } from '../../src/db/client.js'
+
+/**
+ * Single shared sql client used by tests. Same singleton the services use, since
+ * setup.js has already rewritten DATABASE_URL to point at the test schema.
+ */
+export const db = () => getDb()
+
+/**
+ * Truncate Phase 3.7-relevant tables between tests.
+ *
+ * Order matters: pairing_failures FK → payment_sessions; chat_request_notifications
+ * FK → chat_sessions; customer_transactions FK → chat_sessions; etc. Use CASCADE so
+ * we don't have to maintain the topological order when tables get added.
+ *
+ * We deliberately do NOT truncate roles / control_center_users / mitras / customers
+ * — those are seeded once per test file by fixtures and re-truncating them would
+ * force every test to re-create users (slow + noisy).
+ */
+const TRUNCATE_TABLES = [
+  'pairing_failures',
+  'payment_sessions',
+  'chat_request_notifications',
+  'session_extensions',
+  'session_closures',
+  'session_sensitivity_log',
+  'chat_messages',
+  'customer_transactions',
+  'chat_sessions',
+  'auth_sessions',
+  'otp_requests',
+  'mitra_online_logs',
+  'mitra_online_status',
+]
+
+export const resetDb = async () => {
+  const sql = db()
+  // RESTART IDENTITY is a no-op for UUID PKs but cheap; CASCADE handles any future FK additions.
+  await sql.unsafe(`TRUNCATE TABLE ${TRUNCATE_TABLES.join(', ')} RESTART IDENTITY CASCADE`)
+}
+
+/**
+ * Wipe the slow-changing tables too — call sparingly (a single test that needs to
+ * verify "no users" semantics, or in afterAll teardown).
+ */
+export const resetDbHard = async () => {
+  const sql = db()
+  await sql.unsafe(
+    `TRUNCATE TABLE ${TRUNCATE_TABLES.join(', ')}, mitras, customers, control_center_users, roles RESTART IDENTITY CASCADE`
+  )
+}
+
+/**
+ * Drop and re-seed the configurable app_config rows back to their canonical defaults.
+ * Tests that mutate config (e.g. flipping free_trial_enabled) call this in afterEach.
+ */
+export const resetAppConfig = async () => {
+  const sql = db()
+  // Restore the same defaults the migration sets. Using ON CONFLICT … DO UPDATE so a
+  // test-mutated row gets clobbered back, not just left alone.
+  const defaults = [
+    ['anonymity', { enabled: false }],
+    ['max_customers_per_mitra', { value: 3 }],
+    ['free_trial_enabled', { value: true }],
+    ['free_trial_duration_minutes', { value: 5 }],
+    ['extension_timeout_seconds', { value: 60 }],
+    ['early_end_mitra_enabled', { value: false }],
+    ['early_end_customer_enabled', { value: false }],
+    ['payment_session_timeout_minutes', { value: 20 }],
+    ['returning_chat_confirmation_timeout_seconds', { value: 20 }],
+    ['extension_default_action_on_timeout', { value: 'auto_approve' }],
+    ['pairing_blast_timeout_seconds', { value: 60 }],
+  ]
+  for (const [key, value] of defaults) {
+    await sql`
+      INSERT INTO app_config (key, value, updated_at)
+      VALUES (${key}, ${sql.json(value)}, NOW())
+      ON CONFLICT (key) DO UPDATE SET value = EXCLUDED.value, updated_at = NOW()
+    `
+  }
+}