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>

client_app/lib/features/chat/widgets/targeted_waiting_overlay.dart

@@ -0,0 +1,70 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import '../../../core/pairing/pairing_notifier.dart';
+
+/// Full-screen modal overlay shown above the searching screen during the 20s
+/// targeted-mitra wait window. The overlay reads its state directly from the
+/// [PairingTargetedWaitingData] passed in by the parent — the local countdown
+/// ticks are owned by the pairing notifier so the overlay just renders.
+///
+/// "Batalkan" calls `pairingNotifier.cancelSearch()` which posts to
+/// `/api/client/chat/chat-requests/cancel` and transitions state to
+/// `PairingCancelledData`. The parent screen listens for that and pops home.
+class TargetedWaitingOverlay extends ConsumerWidget {
+  final PairingTargetedWaitingData waiting;
+
+  const TargetedWaitingOverlay({super.key, required this.waiting});
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return Container(
+      // Slight scrim so the underlying searching UI is still visible but the
+      // overlay clearly owns the foreground.
+      color: Colors.black.withValues(alpha: 0.55),
+      child: Center(
+        child: Padding(
+          padding: const EdgeInsets.symmetric(horizontal: 32),
+          child: Card(
+            elevation: 6,
+            shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(16)),
+            child: Padding(
+              padding: const EdgeInsets.fromLTRB(24, 24, 24, 16),
+              child: Column(
+                mainAxisSize: MainAxisSize.min,
+                children: [
+                  const SizedBox(
+                    width: 56,
+                    height: 56,
+                    child: CircularProgressIndicator(strokeWidth: 3),
+                  ),
+                  const SizedBox(height: 20),
+                  Text(
+                    'Menunggu konfirmasi ${waiting.mitraName}',
+                    textAlign: TextAlign.center,
+                    style: const TextStyle(fontSize: 18, fontWeight: FontWeight.bold),
+                  ),
+                  const SizedBox(height: 8),
+                  Text(
+                    '${waiting.secondsRemaining}d',
+                    style: const TextStyle(fontSize: 28, fontWeight: FontWeight.w300),
+                  ),
+                  const SizedBox(height: 8),
+                  const Text(
+                    'Bestie punya 20 detik untuk merespon. Kalau tidak ada respon, kami bantu cari bestie lain.',
+                    textAlign: TextAlign.center,
+                    style: TextStyle(fontSize: 13, color: Colors.grey),
+                  ),
+                  const SizedBox(height: 16),
+                  TextButton(
+                    onPressed: () => ref.read(pairingProvider.notifier).cancelSearch(),
+                    child: const Text('Batalkan'),
+                  ),
+                ],
+              ),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}