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/routes/internal/failed-pairings.routes.js

@@ -0,0 +1,69 @@
+import { authenticate, requirePermission } from '../../plugins/auth.js'
+import { getCcUserById } from '../../services/cc-user.service.js'
+import { listFailures, setOperatorAction } from '../../services/pairing-failure.service.js'
+import { UserType, PairingFailureCause, PairingFailureOperatorAction } from '../../constants.js'
+
+const attachCcUser = async (request, reply) => {
+  if (request.auth?.userType !== UserType.CC_USER) {
+    return reply.code(403).send({ success: false, error: { code: 'FORBIDDEN', message: 'Not a control center user' } })
+  }
+  const user = await getCcUserById(request.auth.userId)
+  if (!user) return reply.code(403).send({ success: false, error: { code: 'FORBIDDEN', message: 'Not a control center user' } })
+  request.ccUser = user
+}
+
+const VALID_CAUSE_TAGS = new Set(Object.values(PairingFailureCause))
+const VALID_ACTIONS = new Set(Object.values(PairingFailureOperatorAction))
+
+/**
+ * Control-center "Failed Pairings" review screen backend.
+ *
+ *   GET  /internal/failed-pairings
+ *   POST /internal/failed-pairings/:id/action
+ */
+export const failedPairingsRoutes = async (app) => {
+  app.get('/', {
+    preHandler: [authenticate, attachCcUser, requirePermission('config', 'read')],
+  }, async (request, reply) => {
+    const { cause_tags, date_from, date_to, limit = 50, offset = 0 } = request.query ?? {}
+
+    // cause_tags can arrive as a single string (?cause_tags=foo) or an array
+    // (?cause_tags=foo&cause_tags=bar). Normalize and validate.
+    let causeTagsArr = null
+    if (cause_tags !== undefined) {
+      causeTagsArr = Array.isArray(cause_tags) ? cause_tags : [cause_tags]
+      for (const tag of causeTagsArr) {
+        if (!VALID_CAUSE_TAGS.has(tag)) {
+          return reply.code(422).send({
+            success: false,
+            error: { code: 'VALIDATION_ERROR', message: `Unknown cause_tag: ${tag}` },
+          })
+        }
+      }
+    }
+
+    const result = await listFailures({
+      causeTags: causeTagsArr,
+      dateFrom: date_from || null,
+      dateTo: date_to || null,
+      limit: Number(limit) || 50,
+      offset: Number(offset) || 0,
+    })
+
+    return reply.send({ success: true, data: result })
+  })
+
+  app.post('/:id/action', {
+    preHandler: [authenticate, attachCcUser, requirePermission('config', 'update')],
+  }, async (request, reply) => {
+    const { action } = request.body ?? {}
+    if (!VALID_ACTIONS.has(action)) {
+      return reply.code(422).send({
+        success: false,
+        error: { code: 'VALIDATION_ERROR', message: `action must be one of: ${[...VALID_ACTIONS].join(', ')}` },
+      })
+    }
+    const updated = await setOperatorAction(request.params.id, request.ccUser.id, action)
+    return reply.send({ success: true, data: updated })
+  })
+}