Phase 4 Stage 8: returning-user shell + Tanya Admin sheet

Bestie Choice Sheet on home Mulai Curhat CTA. When the user has at
least one prior session (bestieHistoryHasItemsProvider hits the chat-
sessions history endpoint), the CTA opens a HaloBottomSheet with two
cards: 'bestie yang udah kenal' -> /chat/history, 'bestie baru' ->
/payment/entry. Empty history -> direct to /payment/entry.

Bestie history list visual upgrade: HaloOrb (mitraId seed) + name +
last-session date + topic pills + sessions count + ONLINE pill.
Backend getCustomerHistory now returns topics, mitra_is_online,
sessions_count in a single payload (no per-row presence round-trip).

BestieOfflinePopup with two variants (returning | new_) replacing the
legacy BestieUnavailableDialog. tanya admin ghost CTA on both variants
opens the new TanyaAdminSheet. Stage 5's targeted-wait declined stub
+ Stage 7's chat-screen 409 stub + searching-screen call site all
migrated to the real component.

TanyaAdminSheet: HaloBottomSheet with WA + Telegram buttons, deeplinks
fetched via supportHandlesProvider (CC-config-driven). url_launcher
added to client_app; ios LSApplicationQueriesSchemes covers
https/http/whatsapp/tg.

Stage 2's OTP-blocked popup hubungi admin SnackBar stub also migrated
to TanyaAdminSheet.

Dev-only POST /internal/_test/seed-history-session lets Maestro 08
flow seed a history row before exercising the choice sheet.

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

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

@@ -4,6 +4,7 @@ import 'package:go_router/go_router.dart';
 import '../../../core/pairing/pairing_notifier.dart';
 import '../../../core/theme/halo_tokens.dart';
 import '../../../core/theme/widgets/widgets.dart';
+import '../widgets/bestie_unavailable_dialog.dart';
 
 /// Phase 4 Stage 5 — `SWaitingBestie` overlay.
 ///
@@ -16,9 +17,9 @@ import '../../../core/theme/widgets/widgets.dart';
 ///   The countdown is purely cosmetic; the server owns the auto-reject timer.
 /// - `accepted` (PairingBestieFoundData / PairingActiveData) — routes into
 ///   the chat screen immediately.
-/// - `declined` (PairingTargetedUnavailableData) — shows the bestie-offline
-///   popup. TODO(stage8): swap this stub for the proper BestieOfflinePopup
-///   component once Stage 8 lands.
+/// - `declined` (PairingTargetedUnavailableData) — shows the
+///   [BestieOfflinePopup] returning variant; the popup may offer a
+///   fallback-to-blast CTA when other besties are reachable.
 class TargetedWaitingScreen extends ConsumerStatefulWidget {
   final String mitraId;
   const TargetedWaitingScreen({super.key, required this.mitraId});
@@ -58,21 +59,13 @@ class _TargetedWaitingScreenState extends ConsumerState<TargetedWaitingScreen> {
     }
     if (next is PairingTargetedUnavailableData && !_popupShown) {
       _popupShown = true;
-      // TODO(stage8): replace stub with the production BestieOfflinePopup
-      // (Stage 8 owns the proper variant + fallback-to-blast surface).
       // ignore: discarded_futures
-      HaloPopup.show(
+      BestieOfflinePopup.show(
         context,
-        title: '${next.mitraName} lagi nggak online',
-        body:
-            'bestie kamu belum bisa nerima chat sekarang. coba bestie lain atau balik ke beranda dulu ya.',
-        primary: HaloPopupAction(
-          label: 'kembali ke home',
-          onPressed: () {
-            ref.read(pairingProvider.notifier).reset();
-            if (mounted) context.go('/home');
-          },
-        ),
+        variant: BestieOfflineVariant.returning,
+        mitraName: next.mitraName,
+        paymentSessionId: next.paymentSessionId,
+        topicSensitivity: next.topicSensitivity,
       ).then((_) {
         if (mounted) _popupShown = false;
       });