Phase 5/6 polish: end-session flow, notif sound on API 33+, Xendit webview

Customer end-of-session (figma §6):
- PricingBottomSheet: ghost "cukup, akhiri sesi" CTA + dedup divider
- chat_screen._runEndSessionFlow chains ConfirmEndStep1 → ConfirmEndStep2
  → ClosingMessageSheet (or "lewati saja" → close + /home). The four
  popup/sheet widgets already existed; this commit just wires them
- showModalBottomSheet: showDragHandle=false to suppress the Material 3
  auto-injected handle that was stacking with our own pill

Notification sound on API 33+:
- Bump channel halobestie_chat_v1 → halobestie_chat_v2, created from
  native Kotlin in MainActivity.kt with AudioAttributes contentType
  CONTENT_TYPE_SONIFICATION. flutter_local_notifications' default of
  CONTENT_TYPE_UNKNOWN was causing Android 13 to silently drop audio
  focus while the notification still posted (isNoisy=true). Both apps
- Backend FCM payload channelId updated to v2
- AndroidManifest meta-data: default_notification_icon + color → brand
  silhouette tinted pink instead of generic Android bell. Both apps

Customer pairing reliability:
- pairing_notifier: applyPairedFromPush({sessionId, mitraName}) unsticks
  searching screen when WS push failed and FCM/active-session-poll is
  the first signal. Idempotent across PairingSearchingData,
  PairingTargetedWaitingData, PairingErrorData (covers ALREADY_ACTIVE)
- notification_service: dispatches every FCM data payload to an
  onDataMessage callback (foreground + tap + cold-start). main.dart
  wires that to applyPairedFromPush on type=='paired'. Foreground
  'paired' no longer renders a local banner — screen self-advances
- main.dart activeSession listener also calls applyPairedFromPush when
  a session appears server-side while pairing is in a waiting state.
  Covers stale ALREADY_ACTIVE recovery without a full page refresh

Auth refresh token race:
- auth_notifier._refreshFromStorage shares a single in-flight Future
  across all callers (Auth.build + 401-retry path). Backend rotates
  refresh tokens, so concurrent callers using the same stored token
  would race → loser 401s → catch wipes flutter_secure_storage → user
  appears logged out after kill+reopen

Polish:
- method_pick_screen: resizeToAvoidBottomInset=false — prevents the
  one-frame overflow when entering with the previous screen's keyboard
  still animating out
- bestie_history: BestieHistoryItem now carries `status` (backend
  already returns it). Removed _rawHistoryProvider that fetched the
  same endpoint just to read status; the two providers could go out
  of sync mid-rebuild and throw RangeError(length) on indexing

Xendit Stage 8 (carried from WIP):
- xendit_checkout_screen: embedded webview hosting Xendit's invoice
  page (intercepts halobestie:// deeplink + return-page URLs for
  deterministic pop)
- waiting_payment_screen: auto-pushes the webview when the backend
  payload includes xendit_invoice_url; spinner card + "Buka ulang
  halaman pembayaran" CTA for the QR-fallback path
- pubspec: webview_flutter ^4.13.0

Maestro infra:
- subflows/onboarding_returning_user: drop the "Mulai" carousel wait
  (splash auto-advances since 2026-05-26); tap phone-field hint
  instead of point; drop hideKeyboard (sends BACK → /home when the
  IME isn't actually up)
- New flow ts-customer-06-01-end_session_via_timeup_sheet: drives
  the full path to the chat-expired banner. Last step blocked by a
  Maestro+Flutter gesture quirk on the perpanjang ElevatedButton
  (raw `adb input tap` works at the same coords). Documented in
  memory; deeplink fixture or manual verify recommended
- ChatExpiredBanner button wrapped with Semantics(identifier:
  'chat_extend_button', button: true, onTap: …) — good hygiene for
  future tests even though it doesn't fix the dadb tap issue

.dev/: tracked wsl_emulator_bridge.ps1 + wsl_tcp_relay.py for
Maestro-on-WSL setup (Windows-side netsh portproxy + WSL-side
loopback relays). Both referenced from existing CLAUDE.md notes.

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

mitra_app/lib/core/notifications/notification_service.dart

@@ -12,14 +12,15 @@ class NotificationService {
   /// Set this from the app to bridge notifications → Riverpod state.
   static void Function(String sessionId)? onChatRequestTapped;
 
-  // Channel ID is bumped (`chat_messages` → `halobestie_chat_v1`) because
-  // Android binds notification sound at channel-creation time on API 26+. An
-  // existing `chat_messages` channel still routes through whatever sound was
-  // set when it was first created (system default), so we mint a fresh ID
-  // for the branded sound. Backend FCM payloads target the same ID — see
-  // backend/src/services/notification.service.js.
+  // Channel ID bumped to v2 — v1 was created by flutter_local_notifications
+  // with AudioAttributes content_type=CONTENT_TYPE_UNKNOWN, which Android 13+
+  // silently treats as non-noisy when routing — notifications post and are
+  // tagged isNoisy=true, but systemui never requests audio focus and the
+  // sound never plays. v2 is created natively in MainActivity.kt with
+  // CONTENT_TYPE_SONIFICATION so audio routing works on API 33+. Backend FCM
+  // payloads target this ID — see backend/src/services/notification.service.js.
   static const _channel = AndroidNotificationChannel(
-    'halobestie_chat_v1',
+    'halobestie_chat_v2',
     'Chat HaloBestie',
     description: 'Notifications for incoming chat messages and extension requests',
     importance: Importance.high,
@@ -71,6 +72,12 @@ class NotificationService {
           channelDescription: _channel.description,
           importance: Importance.high,
           priority: Priority.high,
+          // Foreground-path icon override. The OS will tint alpha-only
+          // content with the color set in AndroidManifest's
+          // default_notification_color meta-data. ic_launcher_foreground is
+          // the adaptive icon's foreground layer for the Mitra HaloBestie
+          // logo on transparent.
+          icon: 'ic_launcher_foreground',
           // API 26+ ignores this in favor of the channel's sound; included for
           // the API 24/25 path where channels don't exist yet.
           sound: const RawResourceAndroidNotificationSound('halobestie_notif'),