Phase 4 §4: payment-before-pair for returning users + Maestro suite

Stages 5.1, 5.3, 5.4 of the returning-user flow rework. All three §4
entry paths now require payment BEFORE pairing, matching the updated
mermaid spec.

* Spec (requirement/flow_customer.mermaid.md §4): payment block converges
  three call-sites (bestie-yang-udah-kenal-online, bestie-baru,
  offline-popup → cari bestie lain). PairRoute dispatches lama → targeted
  pair, baru/cari-lain → §3 blast. §3 retains its post-payment-shared
  contract.

* Stage 5.1 (client_app): PaymentDraft carries targetedMitraId +
  topicSensitivity. bestie_history_list seeds the draft + pushes
  /payment/entry (was legacy /payment). searching_screen branches on
  draft.targetedMitraId for blast-vs-targeted dispatch.
  payment_entry uses resetExceptTarget(); bestie_choice_sheet + home
  _onCurhatBestieBaruPressed call explicit reset() before push so
  the keepAlive draft can't leak stale targeting into a blast.

* Stage 5.3 (client_app): new BestieOfflineVariant.prePayReturning.
  Bestie-history-list _BestieRow splits tappable from dim so offline
  rows render dimmed but route taps into the popup. CTA "cari bestie
  lain" resets the draft + pushes /payment/entry.

* Stage 5.4 (client_app): deleted legacy /payment route,
  payment_screen.dart, payment_notifier.dart(+.g.dart). router cleaned.

* Tests (requirement/phase4-customer-flow.md + client_app/.maestro/):
  six Maestro flows TS-01..TS-06 covering every §4 branching point,
  all passing end-to-end. Shared onboarding prelude under
  .maestro/subflows/. New helper scripts: accept_latest_pending,
  force_mitra_offline, force_other_mitra_online,
  reset_all_mitras_online, mitra_accept_latest_internal. New backend
  _test endpoints to match. /reset-phone now cascade-deletes
  customer_transactions (FK was blocking). /force-pairing-timeout
  branches targeted (RETURNING_CHAT_TIMEOUT via
  expireTargetedPairingRequest, now exported) vs blast (PAIRING_FAILED).
  seed_history_session also outputs MITRA_NAME_RE (regex-escaped) for
  reliable selectors against display names containing regex specials.

* mitra_app: dispose-during-deactivate guardrail for back-press on the
  mitra chat screen after the customer's goodbye message. Pending real
  emulator repro verification (carried over from 2026-05-15).

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

client_app/lib/features/chat/screens/searching_screen.dart

@@ -1,7 +1,6 @@
 import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:go_router/go_router.dart';
-import '../../../core/constants.dart';
 import '../../../core/pairing/pairing_notifier.dart';
 import '../../../core/theme/halo_tokens.dart';
 import '../../../core/theme/widgets/widgets.dart';
@@ -44,18 +43,32 @@ class _SearchingScreenState extends ConsumerState<SearchingScreen> {
     ref.listenManual<PairingData>(pairingProvider, _onPairingState);
     WidgetsBinding.instance.addPostFrameCallback((_) {
       if (!mounted) return;
-      // Kick off the blast if pairing hasn't started yet — Phase 4's
-      // multi-screen payment flow lands here without a startSearch call
+      // Kick off pairing if it hasn't started yet — Phase 4's multi-screen
+      // payment flow lands here without an upstream startSearch call
       // (waiting → notif-gate → /chat/searching, no intermediate that
-      // owned the call).
+      // owned the call). Branch on draft.targetedMitraId: a returning-user
+      // "Curhat lagi" flow stamped the targeted mitra onto the draft before
+      // payment, so we fire the targeted request and bounce to the dedicated
+      // wait overlay; everything else is a general blast.
       final state = ref.read(pairingProvider);
       if (state is PairingInitialData) {
         final draft = ref.read(paymentDraftNotifierProvider);
         if (draft.paymentId != null) {
+          if (draft.targetedMitraId != null) {
+            // ignore: discarded_futures
+            ref.read(pairingProvider.notifier).startTargetedSearch(
+                  paymentSessionId: draft.paymentId!,
+                  mitraId: draft.targetedMitraId!,
+                  mitraName: draft.targetedMitraName ?? 'Bestie',
+                  topicSensitivity: draft.topicSensitivity,
+                );
+            context.go('/chat/waiting-targeted/${draft.targetedMitraId}');
+            return;
+          }
           // ignore: discarded_futures
           ref.read(pairingProvider.notifier).startSearch(
                 paymentSessionId: draft.paymentId!,
-                topicSensitivity: TopicSensitivity.regular,
+                topicSensitivity: draft.topicSensitivity,
               );
         }
       }

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

@@ -6,24 +6,31 @@ import '../../../core/constants.dart';
 import '../../../core/pairing/pairing_notifier.dart';
 import '../../../core/theme/halo_tokens.dart';
 import '../../../core/theme/widgets/widgets.dart';
+import '../../payment/state/payment_draft_provider.dart';
 import '../../support/widgets/tanya_admin_sheet.dart';
 
 /// Phase 4 Stage 8 — `BestieOfflinePopup`.
 ///
-/// Two variants:
+/// Three variants:
 /// - [BestieOfflineVariant.returning] — the customer tried to chat with a
 ///   specific mitra (history "Curhat lagi"); the targeted attempt failed
 ///   (409 `targeted_mitra_offline`, or WS `returning_chat_timeout` /
 ///   `returning_chat_rejected`). Payment session is still `confirmed`, so we
 ///   surface a `Chat dengan bestie lain` primary CTA when other besties are
 ///   reachable (calls [Pairing.fallbackToBlast]).
+/// - [BestieOfflineVariant.prePayReturning] — Stage 5.3: the customer tapped
+///   a dimmed (offline) row in `BestieHistoryList` BEFORE any payment. No
+///   payment session exists yet, so the "cari bestie lain" CTA resets the
+///   payment draft and pushes `/payment/entry` for a fresh blast-payment
+///   flow. This branch never calls [Pairing.fallbackToBlast] because there's
+///   no `paymentSessionId` to attach to.
 /// - [BestieOfflineVariant.new_] — the customer triggered a general blast
 ///   that bottomed out (no online besties). No fallback button; just a
 ///   ghost `tanya admin` and a `kembali ke home` exit.
 ///
-/// Both variants expose `tanya admin` via a ghost CTA that opens the
+/// All variants expose `tanya admin` via a ghost CTA that opens the
 /// [TanyaAdminSheet].
-enum BestieOfflineVariant { returning, new_ }
+enum BestieOfflineVariant { returning, prePayReturning, new_ }
 
 class BestieOfflinePopup extends ConsumerWidget {
   final BestieOfflineVariant variant;
@@ -65,8 +72,12 @@ class BestieOfflinePopup extends ConsumerWidget {
     final hasOtherAvailable = availabilityAsync.valueOrNull ?? false;
 
     final isReturning = variant == BestieOfflineVariant.returning;
-    final title = isReturning ? '$mitraName lagi nggak online' : 'semua bestie lagi istirahat';
-    final body = isReturning
+    final isPrePayReturning = variant == BestieOfflineVariant.prePayReturning;
+    final mentionsBestie = isReturning || isPrePayReturning;
+    final title = mentionsBestie
+        ? '$mitraName lagi nggak online'
+        : 'semua bestie lagi istirahat';
+    final body = mentionsBestie
         ? 'bestie kamu belum bisa nerima chat sekarang. coba bestie lain atau balik ke beranda dulu ya.'
         : 'lagi nggak ada bestie yang siap dengerin. coba lagi bentar, atau hubungin admin biar dibantu.';
 
@@ -139,6 +150,19 @@ class BestieOfflinePopup extends ConsumerWidget {
                       );
                 },
               )
+            else if (isPrePayReturning)
+              HaloButton(
+                label: 'cari bestie lain',
+                fullWidth: true,
+                onPressed: () {
+                  // No payment session yet — clear any targeted-mitra intent
+                  // on the draft so the fresh `/payment/entry` flow falls
+                  // through to the blast branch.
+                  ref.read(paymentDraftNotifierProvider.notifier).reset();
+                  Navigator.of(context).pop();
+                  context.push('/payment/entry');
+                },
+              )
             else
               HaloButton(
                 label: 'kembali ke home',
@@ -161,7 +185,7 @@ class BestieOfflinePopup extends ConsumerWidget {
                 TanyaAdminSheet.show(context);
               },
             ),
-            if (canFallbackToBlast) ...[
+            if (canFallbackToBlast || isPrePayReturning) ...[
               const SizedBox(height: HaloSpacing.s4),
               HaloButton(
                 label: 'kembali ke home',