Phase 4 Stage 4: notif gate + home permission-denied banner

Notif Gate full screen at /onboarding/notif-gate, reached from waiting
payment on confirmed/consumed status. Auto-advances to /chat/searching
when permission is already granted; otherwise shows izinkan/nanti aja
HaloButton CTAs. NotifPermission helper wraps firebase_messaging +
permission_handler with readStatus/request/openAppSettings; cached in
notifPermissionStatusProvider that re-reads on app foreground via an
internal WidgetsBindingObserver.

home_screen amber banner above-the-fold when notifPermissionStatusProvider
reports denied. Dismissable for the session via homeNotifBannerDismissedProvider
(in-memory StateProvider, no persistence - cold-restart re-shows).
nyalain CTA -> openAppSettings().

Manifest + Info.plist permission entries added.

Note: main.dart still pre-requests FirebaseMessaging permission at boot,
which can pre-resolve status so the gate auto-advances instead of acting
as the first prompt. Left intact for now; can be removed in a later
stage if the gate should be the first-ask UX.

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

client_app/lib/features/home/home_screen.dart

@@ -4,6 +4,12 @@ import 'package:go_router/go_router.dart';
 import '../../core/auth/auth_notifier.dart';
 import '../../core/availability/mitra_availability_notifier.dart';
 import '../../core/chat/active_session_notifier.dart';
+import '../../core/notifications/notif_permission.dart';
+import '../../core/theme/halo_tokens.dart';
+
+/// Session-only dismiss flag for the "notif denied" banner. Resets on cold
+/// restart by design — `StateProvider` lives in memory only.
+final homeNotifBannerDismissedProvider = StateProvider<bool>((_) => false);
 
 /// Home screen.
 ///
@@ -107,9 +113,13 @@ class _HomeScreenState extends ConsumerState<HomeScreen> with WidgetsBindingObse
         child: ListView(
           // Force-scroll so RefreshIndicator can fire even on a short body.
           physics: const AlwaysScrollableScrollPhysics(),
-          padding: const EdgeInsets.all(32),
+          padding: EdgeInsets.zero,
           children: [
-            const SizedBox(height: 32),
+            const _NotifDeniedBanner(),
+            const Padding(
+              padding: EdgeInsets.symmetric(horizontal: 32),
+              child: SizedBox(height: 32),
+            ),
             Center(child: Text('Halo, $displayName!', style: const TextStyle(fontSize: 24))),
             const SizedBox(height: 32),
             Center(
@@ -235,3 +245,76 @@ class _ActiveSessionCard extends StatelessWidget {
     );
   }
 }
+
+/// Above-the-fold amber banner shown when notif permission is denied. Tap
+/// "nyalain" → opens app settings; tap the close icon → hides for the
+/// in-memory session only (cold restart re-shows it).
+class _NotifDeniedBanner extends ConsumerWidget {
+  const _NotifDeniedBanner();
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final statusAsync = ref.watch(notifPermissionStatusProvider);
+    final dismissed = ref.watch(homeNotifBannerDismissedProvider);
+    final isDenied = statusAsync.valueOrNull == NotifPermStatus.denied;
+    if (!isDenied || dismissed) {
+      return const SizedBox.shrink();
+    }
+    return Container(
+      width: double.infinity,
+      color: HaloTokens.accentSoft,
+      padding: const EdgeInsets.symmetric(
+        horizontal: HaloSpacing.s16,
+        vertical: HaloSpacing.s8,
+      ),
+      child: Row(
+        children: [
+          const Icon(
+            Icons.notifications_off_outlined,
+            size: 18,
+            color: HaloTokens.brandDark,
+          ),
+          const SizedBox(width: HaloSpacing.s8),
+          const Expanded(
+            child: Text(
+              'notifikasi off — kamu bisa kelewat chat dari bestie',
+              style: TextStyle(
+                fontFamily: HaloTokens.fontBody,
+                fontSize: 12.5,
+                color: HaloTokens.ink,
+              ),
+            ),
+          ),
+          TextButton(
+            style: TextButton.styleFrom(
+              foregroundColor: HaloTokens.brandDark,
+              padding: const EdgeInsets.symmetric(
+                horizontal: HaloSpacing.s8,
+              ),
+              minimumSize: const Size(0, 32),
+              tapTargetSize: MaterialTapTargetSize.shrinkWrap,
+              textStyle: const TextStyle(
+                fontFamily: HaloTokens.fontBody,
+                fontSize: 13,
+                fontWeight: FontWeight.w600,
+              ),
+            ),
+            onPressed: () =>
+                ref.read(notifPermissionStatusProvider.notifier).openAppSettings(),
+            child: const Text('nyalain'),
+          ),
+          IconButton(
+            iconSize: 18,
+            visualDensity: VisualDensity.compact,
+            padding: EdgeInsets.zero,
+            constraints: const BoxConstraints(),
+            color: HaloTokens.inkSoft,
+            icon: const Icon(Icons.close),
+            onPressed: () =>
+                ref.read(homeNotifBannerDismissedProvider.notifier).state = true,
+          ),
+        ],
+      ),
+    );
+  }
+}