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/support/providers/support_handles_provider.dart

@@ -0,0 +1,33 @@
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import '../../../core/api/api_client_provider.dart';
+
+class SupportHandle {
+  final String label;
+  final String deeplink;
+  const SupportHandle({required this.label, required this.deeplink});
+
+  factory SupportHandle.fromJson(Map<String, dynamic> json) =>
+      SupportHandle(
+        label: json['label'] as String? ?? '',
+        deeplink: json['deeplink'] as String? ?? '',
+      );
+}
+
+class SupportHandles {
+  final SupportHandle? wa;
+  final SupportHandle? telegram;
+  const SupportHandles({this.wa, this.telegram});
+
+  factory SupportHandles.fromJson(Map<String, dynamic> json) {
+    SupportHandle? parse(dynamic v) =>
+        v is Map<String, dynamic> ? SupportHandle.fromJson(v) : null;
+    return SupportHandles(wa: parse(json['wa']), telegram: parse(json['telegram']));
+  }
+}
+
+final supportHandlesProvider = FutureProvider<SupportHandles>((ref) async {
+  final api = ref.read(apiClientProvider);
+  final response = await api.get('/api/client/support-handles');
+  final data = response['data'] as Map<String, dynamic>? ?? const {};
+  return SupportHandles.fromJson(data);
+});