Mitra Bestie §1–§3: shell + Undangan + popup + chat polish

Brings the mitra app to figma-bestie parity for Home (§1), Undangan
inbox with Curhat Baru + Perpanjang tabs (§2), and the incoming-popup
+ active-chat flow (§3). Home now lives inside a StatefulShellRoute
with BestieTabBar so Profil + Undangan + Home share one shell.

- Shell: features/shell/ (StatefulShellRoute, BestieTabBar, 3 branches)
- Undangan: features/undangan/ — Curhat Baru reads
  chatRequestProvider.pendingInvites; row Terima delegates accept to
  the notifier and ChatRequestOverlay owns nav (no double-push).
  Perpanjang tab stubbed (empty state) until backend exposes
  pendingExtensionsProvider.
- Profil: features/profile/ — Bestie-styled stub
- Home: refactored to body-only (shell owns chrome)
- Popup: chat_request_overlay + chat_request_notifier updated to
  serve the list rows, not just the modal
- Chat: mitra_chat_screen polish
- Theme: accentAmber tokens for the Perpanjang tab + halo_orb widget
  (loading spinner used by undangan list states)
- Login: replace broken GoRouterState location guard with
  _expectOtpPush flag — was stacking duplicate /otp pages on OTP
  resend (see project-otp-nav-bug-fixed-2026-05-21)

Maestro:
- 17 new flows under .maestro/flows/ts-mitra-{1,2,3}-* covering home
  online/offline variants, undangan empty/populated/tolak states,
  popup curhat-baru → accept → chat → ended banner, plus popup
  dismiss/expire/cancelled edge cases
- 4 new §A OTP flows (07/08/09/10) for invalid/mismatch/expired/cooldown
- Helper scripts: force_mitra_online/offline, force_pairing_timeout,
  force_session_expires_at, delete_mitra_status_row,
  customer_blast_now (js), customer_cancel_latest_blast
- Backend: POST /internal/_test/delete-mitra-status-row supports the
  "fresh mitra with no status row" test setup

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

mitra_app/lib/features/shell/shell_screen.dart

@@ -0,0 +1,44 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:go_router/go_router.dart';
+import '../../core/chat/chat_request_notifier.dart';
+import '../../core/theme/halo_tokens.dart';
+import 'widgets/bestie_tab_bar.dart';
+
+/// Shell scaffold for the 3-tab mitra UI: Home / Chat / Profil.
+///
+/// Used as the `builder` of a `StatefulShellRoute.indexedStack` in
+/// `router.dart`. Renders the active branch's navigator in the body and
+/// `BestieTabBar` at the bottom.
+///
+/// Tab content is owned by each branch route — this widget only owns the
+/// scaffold + tab bar.
+class ShellScreen extends ConsumerWidget {
+  const ShellScreen({super.key, required this.navigationShell});
+
+  final StatefulNavigationShell navigationShell;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    // Watch the chat-request state so the badge updates when new requests
+    // arrive (or are accepted/declined). We don't use the value directly —
+    // we want the rebuild trigger, then read the count via the notifier.
+    ref.watch(chatRequestProvider);
+    final chatBadge = ref.read(chatRequestProvider.notifier).activeRequestCount;
+
+    return Scaffold(
+      backgroundColor: HaloTokens.bg,
+      body: navigationShell,
+      bottomNavigationBar: BestieTabBar(
+        activeIndex: navigationShell.currentIndex,
+        chatBadgeCount: chatBadge,
+        onTap: (i) => navigationShell.goBranch(
+          i,
+          // Re-tapping the active tab pops back to the branch root.
+          initialLocation: i == navigationShell.currentIndex,
+        ),
+      ),
+    );
+  }
+}
+