feat: implement mobile UI, Android build configuration, and share intent handling using share_handler

lib/features/sender/presentation/screens/mobile_sender_screen.dart

@@ -3,6 +3,7 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import '../../../../core/theme/app_colors.dart';
 import '../../../discovery/presentation/providers/discovery_providers.dart';
 import '../providers/sender_providers.dart';
+import '../providers/share_handler_provider.dart';
 
 class MobileSenderScreen extends ConsumerStatefulWidget {
   const MobileSenderScreen({super.key});
@@ -14,6 +15,11 @@ class MobileSenderScreen extends ConsumerStatefulWidget {
 class _MobileSenderScreenState extends ConsumerState<MobileSenderScreen> {
   final _urlController = TextEditingController();
 
+  @override
+  void initState() {
+    super.initState();
+  }
+
   @override
   void dispose() {
     _urlController.dispose();
@@ -22,6 +28,9 @@ class _MobileSenderScreenState extends ConsumerState<MobileSenderScreen> {
 
   @override
   Widget build(BuildContext context) {
+    // Initialize share handler
+    ref.watch(shareHandlerProvider);
+    
     final devicesAsync = ref.watch(discoveredDevicesProvider);
     final senderState = ref.watch(senderProvider);