feat(macos): add macOS permissions service for Input Monitoring, Local Network, and Notifications

Add MacOSPermissionsService (Dart) + native MethodChannel handler (Swift)
for macOS-specific permissions not covered by permission_handler:

- Input Monitoring (CGPreflightListenEventAccess /
  CGRequestListenEventAccess) for global PTT via Event Tap
- Local Network Privacy prompt (NWBrowser for _ts3._tcp, macOS 15+)
- Notifications (UNUserNotificationCenter authorization)

Trace: SRS-198, SRS-297, SRS-300, SysRS-166, SDD-091

Changes:
- Info.plist: add NSBonjourServices array with _ts3._tcp
- macos_permissions_service.dart: Dart service with MethodChannel,
  ValueNotifier states, PTT capability derivation (L0Focused /
  L1MacOSEventTap), non-macOS short-circuit
- MainFlutterWindow.swift: native handler registered as FlutterPlugin,
  Input Monitoring check/request/polling, NWBrowser trigger with
  denial detection, UNUserNotificationCenter request
- main.dart: wire service into bootstrap lifecycle, listen for PTT
  capability changes from Input Monitoring state
- macos_permissions_service_test.dart: 17 unit tests covering inbound
  state changes, outbound calls, lifecycle, error handling, platform
  behavior (179/179 full suite pass)

apps/chanora_flutter/lib/main.dart

@@ -23,6 +23,7 @@ import 'services/audio_lifecycle_service.dart';
 import 'services/channel_join_error_mapper.dart';
 import 'services/connection_phase_state.dart';
 import 'services/ios_permissions_service.dart';
+import 'services/macos_permissions_service.dart';
 import 'services/prefetch_debouncer.dart';
 import 'services/snapshot_state_mapper.dart';
 import 'services/ts3_server_link.dart';
@@ -378,6 +379,12 @@ class _BetaHomeState extends State<_BetaHome> with WidgetsBindingObserver {
   final AndroidPermissionsService _androidPermissions =
       AndroidPermissionsService();
   final IosPermissionsService _iosPermissions = IosPermissionsService();
+  // SRS-198 / SRS-297 / SRS-300: macOS Input Monitoring, Local Network,
+  // and Notifications permission service. On non-macOS hosts the service
+  // short-circuits to "granted" / "unsupported" and never wires the
+  // MethodChannel.
+  final MacOSPermissionsService _macOSPermissions =
+      MacOSPermissionsService();
   final UiPreferencesService _uiPreferences = const UiPreferencesService();
 
   @override
@@ -399,6 +406,16 @@ class _BetaHomeState extends State<_BetaHome> with WidgetsBindingObserver {
     _iosPermissions.recordAudioState.addListener(
       _onRecordAudioPermissionChanged,
     );
+    // SRS-198 / SRS-297 / SRS-300: start macOS permission service.
+    // On non-macOS this is a no-op. On macOS, it checks Input
+    // Monitoring state and begins polling for changes so the PTT
+    // capability badge upgrades from L0Focused → L1MacOSEventTap
+    // when the user grants the permission in System Settings.
+    _macOSPermissions.start();
+    _macOSPermissions.checkInitialStates();
+    _macOSPermissions.pttCapabilityState.addListener(
+      _onMacOSPttCapabilityChanged,
+    );
     WidgetsBinding.instance.addPostFrameCallback((_) {
       unawaited(_requestRecordAudioOnStartup());
     });
@@ -498,6 +515,26 @@ class _BetaHomeState extends State<_BetaHome> with WidgetsBindingObserver {
     }
   }
 
+  /// SRS-198 / SRS-297 / SRS-300 / SDD-091: React to macOS Input
+  /// Monitoring state changes by updating the PTT capability level.
+  /// When the macOS permissions service detects that Input Monitoring
+  /// has been granted (via polling), it emits `L1MacOSEventTap` which
+  /// overrides the bridge-emitted `L0Focused` default.
+  void _onMacOSPttCapabilityChanged() {
+    final level = _macOSPermissions.pttCapabilityState.value;
+    // Only override if the macOS service has a resolved state
+    // different from the current bridge-emitted level, and only
+    // on macOS.
+    if (_isMacOS && level != _pttLevel) {
+      setState(() {
+        _pttLevel = level;
+        if (level == 'L1MacOSEventTap') {
+          _pttBackendId = 'macos-event-tap';
+        }
+      });
+    }
+  }
+
   Future<void> _clearPermissionHardMute() async {
     if (!_hardMuteByPermission || _permissionHardMuteClearInFlight) return;
     _permissionHardMuteClearInFlight = true;
@@ -936,11 +973,16 @@ class _BetaHomeState extends State<_BetaHome> with WidgetsBindingObserver {
     _iosPermissions.recordAudioState.removeListener(
       _onRecordAudioPermissionChanged,
     );
+    // SRS-198 / SRS-297: detach macOS permission listeners.
+    _macOSPermissions.pttCapabilityState.removeListener(
+      _onMacOSPttCapabilityChanged,
+    );
     // SDD-106: detach the Kotlin -> Dart MethodChannel handler so a
     // late invokeMethod from the platform side cannot land on this
     // disposed state.
     _androidPermissions.stop();
     _iosPermissions.stop();
+    _macOSPermissions.stop();
     super.dispose();
   }