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/jwt.js

@@ -0,0 +1,42 @@
+import jwt from 'jsonwebtoken'
+import { randomUUID } from 'node:crypto'
+import { UserType } from '../../src/constants.js'
+
+/**
+ * Mint a JWT that the production `authenticate` plugin will accept. Mirrors the
+ * payload shape from src/services/token.service.js#signAccessToken.
+ *
+ * We deliberately do NOT call issueTokens (which writes an auth_sessions row) so
+ * tests stay independent of that table. The access-token verification path in
+ * production never reads the DB — it only validates the JWT signature + claims.
+ *
+ * sessionId defaults to a random UUID; pass an explicit one if a test asserts on
+ * the session_id value.
+ */
+const sign = ({ userType, userId, sessionId = randomUUID() }) => {
+  const secret = process.env.AUTH_JWT_SECRET
+  if (!secret || secret.length < 32) {
+    throw new Error('AUTH_JWT_SECRET missing or too short for test JWT minting')
+  }
+  return jwt.sign(
+    { user_type: userType, session_id: sessionId },
+    secret,
+    {
+      algorithm: 'HS256',
+      expiresIn: 3600,
+      subject: userId,
+    },
+  )
+}
+
+export const customerJwt = (userId, opts = {}) =>
+  sign({ userType: UserType.CUSTOMER, userId, ...opts })
+
+export const mitraJwt = (userId, opts = {}) =>
+  sign({ userType: UserType.MITRA, userId, ...opts })
+
+export const ccJwt = (userId, opts = {}) =>
+  sign({ userType: UserType.CC_USER, userId, ...opts })
+
+/** `Authorization: Bearer …` header builder for app.inject calls. */
+export const authHeader = (token) => ({ authorization: `Bearer ${token}` })