Phase 4 Stage 3: payment shell (multi-screen flow)

Six new screens under /payment/* + a paymentDraftProvider holding
mode/durationId/durationMinutes/priceIDR/paymentId/isFirstSessionDiscount
across the flow. PaymentEntryScreen handles the routing decision
(eligible+enabled -> /payment/discount-paywall, else /payment/method-pick)
and clears the draft on fresh entry.

Screens:
- discount_paywall_screen: S6 first-session discount with struck-through
  gimmick price + actual price + 'mulai · Rp{actual}' CTA -> /payment/method
- method_pick_screen: chat vs call cards
- duration_pick_screen: tier list with chat|call mode toggle that resets
  the selection on swap
- payment_method_screen: QRIS-first list, posts to existing
  /api/client/payment-sessions with mode/duration/price/discount/method
- waiting_payment_screen: qr_flutter QR (encodes paymentId in mock mode),
  20-min countdown header, 3s polling for status, pauses on background
  via WidgetsBindingObserver
- payment_expired_screen: retry CTA -> /payment/method with draft retained

Status mapping: real payment_sessions.status uses 'confirmed'/'consumed'
for paid (not 'paid' as in plan) and 'expired'/'abandoned' as terminal.

home_screen 'Mulai Curhat' CTA now pushes /payment/entry.

Dev-only /internal/_test/force-expire-payment endpoint to drive Maestro
flow 04_payment_expired.yaml without waiting 20 minutes. Gated behind
NODE_ENV !== 'production'.

chat_opening_provider PricingData extended to carry Phase 4 chat/call
groups + firstSessionDiscount, back-compat with the Phase 3 shape.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

client_app/lib/features/payment/screens/payment_expired_screen.dart

@@ -0,0 +1,94 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:go_router/go_router.dart';
+import '../../../core/theme/halo_tokens.dart';
+import '../../../core/theme/widgets/halo_button.dart';
+
+/// "Pembayaran expired" — terminal screen for the timeout path. The retry CTA
+/// pushes back to `/payment/method`; the draft is intentionally retained so
+/// the user re-pays the same plan/mode/discount without re-picking.
+class PaymentExpiredScreen extends ConsumerWidget {
+  final String paymentId;
+  const PaymentExpiredScreen({super.key, required this.paymentId});
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return PopScope(
+      canPop: true,
+      child: Scaffold(
+        backgroundColor: HaloTokens.bg,
+        body: SafeArea(
+          child: Padding(
+            padding: const EdgeInsets.fromLTRB(
+              HaloSpacing.s24,
+              HaloSpacing.s32,
+              HaloSpacing.s24,
+              HaloSpacing.s32,
+            ),
+            child: Column(
+              children: [
+                Expanded(
+                  child: Column(
+                    mainAxisAlignment: MainAxisAlignment.center,
+                    children: [
+                      Container(
+                        width: 90,
+                        height: 90,
+                        decoration: const BoxDecoration(
+                          color: Color(0xFFFFE5E5),
+                          borderRadius: HaloRadius.xl,
+                        ),
+                        alignment: Alignment.center,
+                        child: const Text('⏰', style: TextStyle(fontSize: 42)),
+                      ),
+                      const SizedBox(height: HaloSpacing.s20),
+                      const Text(
+                        'pembayaran kedaluwarsa',
+                        textAlign: TextAlign.center,
+                        style: TextStyle(
+                          fontFamily: HaloTokens.fontDisplay,
+                          fontSize: 22,
+                          fontWeight: FontWeight.w700,
+                          color: HaloTokens.brandDark,
+                          height: 1.25,
+                          letterSpacing: -0.5,
+                        ),
+                      ),
+                      const SizedBox(height: HaloSpacing.s12),
+                      const SizedBox(
+                        width: 280,
+                        child: Text(
+                          'sesi pembayaran udah lewat 20 menit. coba lagi yuk, gak ada potongan apapun.',
+                          textAlign: TextAlign.center,
+                          style: TextStyle(
+                            fontSize: 13.5,
+                            color: HaloTokens.inkSoft,
+                            height: 1.55,
+                          ),
+                        ),
+                      ),
+                    ],
+                  ),
+                ),
+                HaloButton(
+                  label: 'coba lagi',
+                  size: HaloButtonSize.lg,
+                  fullWidth: true,
+                  onPressed: () => context.go('/payment/method'),
+                ),
+                const SizedBox(height: HaloSpacing.s8),
+                HaloButton(
+                  label: 'kembali ke home',
+                  variant: HaloButtonVariant.ghost,
+                  size: HaloButtonSize.md,
+                  fullWidth: true,
+                  onPressed: () => context.go('/home'),
+                ),
+              ],
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}