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/screens/no_bestie_screen.dart

@@ -1,36 +1,64 @@
 import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:go_router/go_router.dart';
+import '../../../core/pairing/pairing_notifier.dart';
 
-class NoBestieScreen extends StatelessWidget {
+/// Terminal failed-pairing screen.
+///
+/// Reached when the pairing notifier transitions to [PairingFailedData]
+/// (terminal — payment session is `failed_pairing` server-side, audit row
+/// recorded). Copy is intentionally identical regardless of `cause_tag` for
+/// now (the design pass will revise this later).
+///
+/// Single CTA "Kembali ke beranda" resets the pairing notifier and routes
+/// home. PopScope falls back to home for deep-link entry per project memory
+/// rule "Deep-link pop fallback".
+class NoBestieScreen extends ConsumerWidget {
   const NoBestieScreen({super.key});
 
   @override
-  Widget build(BuildContext context) {
-    return Scaffold(
-      body: Center(
-        child: Padding(
-          padding: const EdgeInsets.all(32),
-          child: Column(
-            mainAxisAlignment: MainAxisAlignment.center,
-            children: [
-              const Icon(Icons.sentiment_dissatisfied, size: 80, color: Colors.orange),
-              const SizedBox(height: 24),
-              const Text(
-                'Bestie belum tersedia',
-                style: TextStyle(fontSize: 24, fontWeight: FontWeight.bold),
+  Widget build(BuildContext context, WidgetRef ref) {
+    return PopScope(
+      canPop: true,
+      onPopInvokedWithResult: (didPop, _) {
+        if (!didPop) return;
+        ref.read(pairingProvider.notifier).reset();
+      },
+      child: Scaffold(
+        body: SafeArea(
+          child: Center(
+            child: Padding(
+              padding: const EdgeInsets.all(32),
+              child: Column(
+                mainAxisAlignment: MainAxisAlignment.center,
+                children: [
+                  const Icon(Icons.sentiment_dissatisfied, size: 80, color: Colors.orange),
+                  const SizedBox(height: 24),
+                  const Text(
+                    'Belum berhasil terhubung',
+                    style: TextStyle(fontSize: 22, fontWeight: FontWeight.bold),
+                  ),
+                  const SizedBox(height: 12),
+                  const Text(
+                    'Maaf, kami tidak bisa menemukan bestie untuk sesimu. '
+                    'Tim kami akan menghubungimu segera.',
+                    textAlign: TextAlign.center,
+                    style: TextStyle(fontSize: 16, color: Colors.grey),
+                  ),
+                  const SizedBox(height: 48),
+                  ElevatedButton(
+                    style: ElevatedButton.styleFrom(
+                      padding: const EdgeInsets.symmetric(horizontal: 32, vertical: 14),
+                    ),
+                    onPressed: () {
+                      ref.read(pairingProvider.notifier).reset();
+                      context.go('/home');
+                    },
+                    child: const Text('Kembali ke beranda'),
+                  ),
+                ],
               ),
-              const SizedBox(height: 8),
-              const Text(
-                'Maaf, semua Bestie sedang sibuk. Coba lagi nanti ya.',
-                textAlign: TextAlign.center,
-                style: TextStyle(fontSize: 16, color: Colors.grey),
-              ),
-              const SizedBox(height: 48),
-              ElevatedButton(
-                onPressed: () => context.go('/home'),
-                child: const Text('Kembali'),
-              ),
-            ],
+            ),
           ),
         ),
       ),