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>

client_app/pubspec.lock

@@ -1412,6 +1412,38 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "3.0.3"
+  webview_flutter:
+    dependency: "direct main"
+    description:
+      name: webview_flutter
+      sha256: a3da219916aba44947d3a5478b1927876a09781174b5a2b67fa5be0555154bf9
+      url: "https://pub.dev"
+    source: hosted
+    version: "4.13.1"
+  webview_flutter_android:
+    dependency: transitive
+    description:
+      name: webview_flutter_android
+      sha256: ad5182eff9a550925330cb9f0cb038eddfdd5712aba8b77aa0f0400e50f6e688
+      url: "https://pub.dev"
+    source: hosted
+    version: "4.12.0"
+  webview_flutter_platform_interface:
+    dependency: transitive
+    description:
+      name: webview_flutter_platform_interface
+      sha256: "1221c1b12f5278791042f2ec2841743784cf25c5a644e23d6680e5d718824f04"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.15.1"
+  webview_flutter_wkwebview:
+    dependency: transitive
+    description:
+      name: webview_flutter_wkwebview
+      sha256: "82648217f537573e1ca9ae9952d3eacedca6ab5aee69dc84445fc763766dcea2"
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.25.1"
   win32:
     dependency: transitive
     description: