fix(navigation): Ensure context is mounted before navigation and improve error handling

lib/core/services/app_intents_service.dart

@@ -370,7 +370,7 @@ class AppIntentCoordinator extends _$AppIntentCoordinator {
     await Future<void>.delayed(const Duration(milliseconds: 50));
 
     final context = NavigationService.navigatorKey.currentContext;
-    if (context == null) {
+    if (context == null || !context.mounted) {
       throw StateError('Navigation context not available.');
     }
 
@@ -378,6 +378,7 @@ class AppIntentCoordinator extends _$AppIntentCoordinator {
     FocusScope.of(context).unfocus();
 
     // Navigate to voice call page with new conversation flag
+    if (!context.mounted) return;
     await Navigator.of(context).push(
       MaterialPageRoute(
         builder: (_) => const VoiceCallPage(startNewConversation: true),

lib/features/chat/widgets/modern_chat_input.dart

@@ -1965,7 +1965,7 @@ class _ModernChatInputState extends ConsumerState<ModernChatInput>
                             height: IconSize.small + 1,
                             color: iconUrl.endsWith('.svg') ? iconColor : null,
                             colorBlendMode: BlendMode.srcIn,
-                            errorBuilder: (_, __, ___) => Icon(
+                            errorBuilder: (_, _, _) => Icon(
                               icon,
                               size: IconSize.small + 1,
                               color: iconColor,
@@ -2732,7 +2732,7 @@ class _ModernChatInputState extends ConsumerState<ModernChatInput>
                 fit: BoxFit.cover,
                 color: iconUrl.endsWith('.svg') ? iconColor : null,
                 colorBlendMode: BlendMode.srcIn,
-                errorBuilder: (_, __, ___) => Icon(
+                errorBuilder: (_, _, _) => Icon(
                   Platform.isIOS ? CupertinoIcons.sparkles : Icons.auto_awesome,
                   color: iconColor,
                   size: IconSize.modal,