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/fixtures.js

@@ -0,0 +1,64 @@
+import { randomUUID } from 'node:crypto'
+import { db, resetAppConfig } from './db.js'
+
+/**
+ * Insert a customer row. Defaults to the schema after the Phase 3.4 auth rewrite
+ * (display_name nullable, is_anonymous defaults true).
+ */
+export const createCustomer = async ({
+  id = randomUUID(),
+  callName = `TestCust-${id.slice(0, 6)}`,
+  phone = null,
+  isAnonymous = false,
+} = {}) => {
+  const sql = db()
+  const [row] = await sql`
+    INSERT INTO customers (id, display_name, phone, is_anonymous)
+    VALUES (${id}, ${callName}, ${phone}, ${isAnonymous})
+    RETURNING id, display_name, phone, is_anonymous, created_at
+  `
+  return row
+}
+
+/**
+ * Insert a mitra row. If `isOnline` is true, also creates the mitra_online_status row
+ * so pairing.findAvailableMitras includes it.
+ */
+export const createMitra = async ({
+  id = randomUUID(),
+  callName = `TestMitra-${id.slice(0, 6)}`,
+  phone = null,
+  isActive = true,
+  isOnline = false,
+} = {}) => {
+  const sql = db()
+  // mitras.phone is NOT NULL UNIQUE — synthesize a unique phone if not given.
+  const finalPhone = phone || `+62800${Math.floor(Math.random() * 1e10).toString().padStart(10, '0')}`
+  const [row] = await sql`
+    INSERT INTO mitras (id, display_name, phone, is_active)
+    VALUES (${id}, ${callName}, ${finalPhone}, ${isActive})
+    RETURNING id, display_name, phone, is_active, created_at
+  `
+  if (isOnline) {
+    const now = new Date()
+    await sql`
+      INSERT INTO mitra_online_status (mitra_id, is_online, last_online_at, last_heartbeat_at, updated_at)
+      VALUES (${id}, true, ${now}, ${now}, ${now})
+      ON CONFLICT (mitra_id) DO UPDATE
+        SET is_online = true, last_online_at = ${now}, last_heartbeat_at = ${now}, updated_at = ${now}
+    `
+  }
+  return row
+}
+
+/**
+ * Reset app_config rows to their canonical defaults. Tests that mutate config call
+ * this in afterEach (or rely on the global beforeEach in resetAll).
+ */
+export const seedDefaultConfig = () => resetAppConfig()
+
+/**
+ * Convenience: full reset between tests. Truncates Phase 3.7 tables, restores
+ * default config rows.
+ */
+export { resetDb, resetDbHard, resetAppConfig } from './db.js'