fix: resolve web build failures

- Update SDK constraint to >=3.0.0 <4.0.0 (Flutter stable uses Dart 3.x)
- Remove flutter_email_sender (no web support) — replace with mailto: via url_launcher
- support.dart: unified _sendEmail works on both web and mobile

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/src/presentation/screens/support.dart

@@ -1,7 +1,5 @@
 import 'package:community_material_icon/community_material_icon.dart';
-import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
-import 'package:flutter_email_sender/flutter_email_sender.dart';
 import 'package:prosappco/src/components/pop_appbar.dart';
 import 'package:prosappco/src/models/setting_model.dart';
 import 'package:url_launcher/url_launcher.dart';
@@ -26,21 +24,8 @@ class SsupportStateScreen extends State<SupportScreen> {
   }
 
   Future<void> _sendEmail(String recipients) async {
-    final Email email = Email(
-      body: body,
-      subject: subject,
-      recipients: [recipients],
-      isHTML: false,
-    );
-
-    await FlutterEmailSender.send(email);
-  }
-
-  void _sendEmailWeb(String recipients) async {
-    final email = 'mailto:$recipients?subject=${Uri.encodeComponent(recipients)}&body=${Uri.encodeComponent(body)}';
-    if (await canLaunch(email)) {
-      await launch(email);
-    } else {}
+    final uri = 'mailto:$recipients?subject=${Uri.encodeComponent(subject)}&body=${Uri.encodeComponent(body)}';
+    if (await canLaunch(uri)) await launch(uri);
   }
 
   @override
@@ -105,13 +90,7 @@ class SsupportStateScreen extends State<SupportScreen> {
               ),
               const SizedBox(width: 20),
               ElevatedButton(
-                onPressed: () {
-                  if (kIsWeb) {
-                    _sendEmailWeb(settings?.email ?? '');
-                  } else {
-                    _sendEmail(settings?.email ?? '');
-                  }
-                },
+                onPressed: () => _sendEmail(settings?.email ?? ''),
                 style: ElevatedButton.styleFrom(
                   foregroundColor: Colors.white,
                   backgroundColor: const Color(0xFF2BA4EC),