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/payment/state/payment_draft_provider.dart

@@ -1,4 +1,6 @@
+import 'package:flutter/foundation.dart';
 import 'package:riverpod_annotation/riverpod_annotation.dart';
+import '../../../core/constants.dart';
 
 part 'payment_draft_provider.g.dart';
 
@@ -31,6 +33,21 @@ class PaymentDraft {
   final String? paymentId;
   final bool isFirstSessionDiscount;
 
+  /// When set, this payment is for a "Curhat lagi" (returning-targeted) flow:
+  /// downstream of payment confirm, `searching_screen` will fire the targeted
+  /// chat request against this specific mitra rather than the general blast.
+  /// Set by `BestieHistoryListScreen` BEFORE pushing `/payment/entry`.
+  final String? targetedMitraId;
+
+  /// Optional display name for the targeted mitra — surfaced on the targeted
+  /// waiting overlay ("lagi nungguin {name}") and any future returning-flow UI
+  /// that wants to greet the customer with the right bestie.
+  final String? targetedMitraName;
+
+  /// Topic-sensitivity choice made before entering the payment flow. Carried
+  /// through to the eventual chat-request API call. Defaults to `regular`.
+  final TopicSensitivity topicSensitivity;
+
   const PaymentDraft({
     this.mode = PaymentMode.chat,
     this.durationId,
@@ -38,6 +55,9 @@ class PaymentDraft {
     this.priceIDR,
     this.paymentId,
     this.isFirstSessionDiscount = false,
+    this.targetedMitraId,
+    this.targetedMitraName,
+    this.topicSensitivity = TopicSensitivity.regular,
   });
 
   PaymentDraft copyWith({
@@ -47,6 +67,9 @@ class PaymentDraft {
     int? priceIDR,
     String? paymentId,
     bool? isFirstSessionDiscount,
+    String? targetedMitraId,
+    String? targetedMitraName,
+    TopicSensitivity? topicSensitivity,
   }) {
     return PaymentDraft(
       mode: mode ?? this.mode,
@@ -55,6 +78,9 @@ class PaymentDraft {
       priceIDR: priceIDR ?? this.priceIDR,
       paymentId: paymentId ?? this.paymentId,
       isFirstSessionDiscount: isFirstSessionDiscount ?? this.isFirstSessionDiscount,
+      targetedMitraId: targetedMitraId ?? this.targetedMitraId,
+      targetedMitraName: targetedMitraName ?? this.targetedMitraName,
+      topicSensitivity: topicSensitivity ?? this.topicSensitivity,
     );
   }
 }
@@ -103,9 +129,45 @@ class PaymentDraftNotifier extends _$PaymentDraftNotifier {
     state = state.copyWith(paymentId: paymentId);
   }
 
-  /// Wipe the draft when entering the flow fresh (e.g. tapping "Mulai Curhat"
-  /// from home). Keeping it across back-nav inside the flow is the default.
+  /// Mark this draft as a targeted "Curhat lagi" flow against a specific
+  /// mitra. Must be called BEFORE pushing `/payment/entry` from the
+  /// bestie-history list — the entry screen calls [resetExceptTarget] to
+  /// clear stale tier/payment state while preserving the targeting set here.
+  void setTargetedMitra({required String mitraId, String? mitraName}) {
+    state = state.copyWith(
+      targetedMitraId: mitraId,
+      targetedMitraName: mitraName,
+    );
+  }
+
+  /// Set the topic-sensitivity choice for the upcoming chat request.
+  void setTopicSensitivity(TopicSensitivity topicSensitivity) {
+    state = state.copyWith(topicSensitivity: topicSensitivity);
+  }
+
+  /// Full reset — clears EVERYTHING including targeted-mitra intent.
+  /// Use this when starting a fresh BLAST flow (e.g. "bestie baru" branch or
+  /// the no-history Home CTA). If you want to preserve a targeted-mitra
+  /// selection made just before entering the payment flow (set via
+  /// [setTargetedMitra]), use [resetExceptTarget] instead.
   void reset() {
+    debugPrint('[PaymentDraft] reset() — clearing entire draft including targeted-mitra intent');
     state = const PaymentDraft();
   }
+
+  /// Reset everything EXCEPT the targeted-mitra fields. Used by the payment
+  /// entry screen so a fresh dive into the multi-screen flow clears any stale
+  /// tier/payment state while preserving the just-picked targeted mitra. If
+  /// the draft has no targeted mitra set, this behaves identically to
+  /// [reset].
+  void resetExceptTarget() {
+    debugPrint(
+      '[PaymentDraft] resetExceptTarget() — preserving targetedMitraId=${state.targetedMitraId}',
+    );
+    state = PaymentDraft(
+      targetedMitraId: state.targetedMitraId,
+      targetedMitraName: state.targetedMitraName,
+      topicSensitivity: state.topicSensitivity,
+    );
+  }
 }