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/home/screens/bestie_history_list_screen.dart

@@ -5,6 +5,8 @@ import '../../../core/api/api_client_provider.dart';
 import '../../../core/constants.dart';
 import '../../../core/theme/halo_tokens.dart';
 import '../../../core/theme/widgets/widgets.dart';
+import '../../chat/widgets/bestie_unavailable_dialog.dart';
+import '../../payment/state/payment_draft_provider.dart';
 import '../providers/bestie_history_provider.dart';
 
 /// `BestieHistoryList` — the picker for the returning-user "curhat lagi"
@@ -15,14 +17,19 @@ import '../providers/bestie_history_provider.dart';
 /// lives in the Chat-tab Selesai sub-tab, not here.
 ///
 /// Row interaction rules:
-///   - mitra_is_online + status != closing → tap targets `/payment` with
-///     `targetedMitraId`, which jumps into the Stage-3.x payment flow and,
-///     once confirmed, the Stage-5 targeted-wait overlay.
+///   - mitra_is_online + status != closing → tap stamps the picked mitra
+///     onto `paymentDraftNotifierProvider` (via `setTargetedMitra`) and
+///     pushes `/payment/entry`. The Phase-4 multi-screen payment flow
+///     (entry → method-pick → duration-pick → method → waiting → notif-gate
+///     → searching) reads the targeting back off the draft to fire the
+///     returning-chat request after the customer pays.
 ///   - status == closing → tap drops into the chat session screen so the
 ///     user can finish the goodbye composer (one-time grace path).
-///   - mitra_is_online == false → row is dimmed and tap is disabled. Mermaid
-///     §4 calls for a Bestie Offline Popup variant here, deferred until
-///     OfflinePopup gets its returning-user copy.
+///   - mitra_is_online == false → row stays dimmed for the visual cue, but
+///     tap is enabled and opens [BestieOfflinePopup] with the
+///     [BestieOfflineVariant.prePayReturning] variant (Stage 5.3). The popup
+///     offers "cari bestie lain" (resets the draft + pushes `/payment/entry`
+///     for a fresh blast-payment flow) and `tanya admin`.
 class BestieHistoryListScreen extends ConsumerWidget {
   const BestieHistoryListScreen({super.key});
 
@@ -116,12 +123,29 @@ class BestieHistoryListScreen extends ConsumerWidget {
                       );
                       return;
                     }
+                    // Offline mitra — surface the Stage 5.3 pre-payment
+                    // popup. The popup's "cari bestie lain" CTA resets the
+                    // draft and pushes `/payment/entry` for a blast flow.
+                    if (!item.mitraIsOnline) {
+                      // ignore: discarded_futures
+                      BestieOfflinePopup.show(
+                        context,
+                        variant: BestieOfflineVariant.prePayReturning,
+                        mitraName: item.mitraName,
+                      );
+                      return;
+                    }
                     if (item.mitraId == null) return;
-                    context.push('/payment', extra: <String, dynamic>{
-                      'targetedMitraId': item.mitraId,
-                      'mitraName': item.mitraName,
-                      'topicSensitivity': TopicSensitivity.regular,
-                    });
+                    // Stamp the targeted mitra onto the payment draft; the
+                    // multi-screen payment flow (entry → method → waiting →
+                    // notif-gate → searching) reads it back to fire the
+                    // returning-chat request after payment confirms.
+                    ref.read(paymentDraftNotifierProvider.notifier)
+                        .setTargetedMitra(
+                          mitraId: item.mitraId!,
+                          mitraName: item.mitraName,
+                        );
+                    context.push('/payment/entry');
                   },
                 );
               },
@@ -156,15 +180,22 @@ class _BestieRow extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final canPick = item.mitraIsOnline && !isClosing && item.mitraId != null;
+    // Online + has mitraId → full-colour, taps into targeted-pair payment.
+    // Closing → full-colour, taps into the goodbye composer (mitraId may be
+    // absent but `sessionId` is what the chat route needs).
+    // Offline → dim, but still tappable so [BestieOfflinePopup] can fire the
+    // Stage 5.3 pre-payment branch.
+    final isLive = item.mitraIsOnline && item.mitraId != null;
+    final tappable = isLive || isClosing || !item.mitraIsOnline;
+    final dim = !isLive && !isClosing;
     return Material(
       color: HaloTokens.surface,
       borderRadius: HaloRadius.lg,
       child: InkWell(
-        onTap: canPick ? onPick : null,
+        onTap: tappable ? onPick : null,
         borderRadius: HaloRadius.lg,
         child: Opacity(
-          opacity: canPick ? 1.0 : 0.55,
+          opacity: dim ? 0.55 : 1.0,
           child: Padding(
             padding: const EdgeInsets.all(HaloSpacing.s16),
             child: Row(
@@ -239,7 +270,7 @@ class _BestieRow extends StatelessWidget {
                   '→',
                   style: TextStyle(
                     fontSize: 16,
-                    color: canPick ? HaloTokens.brand : HaloTokens.inkMuted,
+                    color: dim ? HaloTokens.inkMuted : HaloTokens.brand,
                   ),
                 ),
               ],