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/src/server.js

@@ -4,6 +4,7 @@ import { buildInternalApp } from './app.internal.js'
 import { autoOfflineStaleMitras } from './services/mitra-status.service.js'
 import { initFirebase } from './plugins/firebase.js'
 import { restoreActiveTimers } from './services/session-timer.service.js'
+import { expireStalePaymentSessions } from './services/payment.service.js'
 
 const PUBLIC_PORT = process.env.PUBLIC_PORT || 3000
 const INTERNAL_PORT = process.env.INTERNAL_PORT || 3001
@@ -32,6 +33,21 @@ const start = async () => {
       console.error('Auto-offline check failed:', err)
     }
   }, 30_000)
+
+  // Expire stale payment_sessions (every 60s).
+  // Pending past expires_at → expired (no failure row). Confirmed-but-stale → failed_pairing
+  // with cause = payment_session_expired (writes a pairing_failures row).
+  // Single-instance for now; Valkey keyspace notifications when we go multi-instance.
+  setInterval(async () => {
+    try {
+      const result = await expireStalePaymentSessions()
+      if (result.expired > 0 || result.failed > 0) {
+        console.log(`Payment sweeper: ${result.expired} expired, ${result.failed} failed_pairing`)
+      }
+    } catch (err) {
+      console.error('Payment session sweeper failed:', err)
+    }
+  }, 60_000)
 }
 
 start().catch((err) => {