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/auth/widgets/otp_blocked_popup.dart

@@ -2,12 +2,13 @@ import 'package:flutter/material.dart';
 import 'package:go_router/go_router.dart';
 import '../../../core/theme/halo_tokens.dart';
 import '../../../core/theme/widgets/widgets.dart';
+import '../../support/widgets/tanya_admin_sheet.dart';
 
 /// Modal shown when OTP delivery / verification is exhausted (rate-limited
 /// 429 from `OTP_RATE_LIMIT_PHONE`, `OTP_RATE_LIMIT_IP`, `OTP_COOLDOWN`, or
 /// `OTP_ATTEMPTS_EXCEEDED`). Offers a "lanjut tanpa verif" exit into the
-/// anonymous flow (preserving any ESP/USP state) and a stub "hubungi admin"
-/// affordance — Stage 8 will wire the real Tanya Admin sheet.
+/// anonymous flow (preserving any ESP/USP state) and a "hubungi admin" CTA
+/// that opens the Tanya Admin sheet.
 class OtpBlockedPopup {
   const OtpBlockedPopup._();
 
@@ -44,12 +45,8 @@ class OtpBlockedPopup {
       secondary: HaloPopupAction(
         label: 'hubungi admin',
         onPressed: () {
-          // TODO(stage8): replace with Tanya Admin sheet.
-          ScaffoldMessenger.of(context).showSnackBar(
-            const SnackBar(
-              content: Text('Tanya Admin akan tersedia segera.'),
-            ),
-          );
+          // ignore: discarded_futures
+          TanyaAdminSheet.show(context);
         },
       ),
     );