Hide donation link on iOS to satisfy App Store guideline 3.1.1

External 'Buy us a coffee' (Buy Me a Coffee) link triggered Apple
rejection under 3.1.1. Gate the About-section tile behind a platform
check so it's omitted on iOS while remaining on Android/Web, where
external donation links are permitted.

Author: MrAlders0n

lib/screens/settings_screen.dart

@@ -818,12 +818,15 @@ class _SettingsScreenState extends State<SettingsScreen> {
                   'Built with contributions from the Greater Ottawa Mesh Radio Enthusiasts community'),
               onTap: () => _launchUrl('https://ottawamesh.ca/'),
             ),
-            ListTile(
-              leading: const Icon(Icons.coffee),
-              title: const Text('Buy us a coffee'),
-              subtitle: const Text('Support MeshMapper development'),
-              onTap: () => _launchUrl('https://buymeacoffee.com/meshmapper'),
-            ),
+            // Buy Me a Coffee — external donation links are fine on Android/Web
+            // but violate Apple guideline 3.1.1 on iOS, so omit it on iOS.
+            if (kIsWeb || defaultTargetPlatform != TargetPlatform.iOS)
+              ListTile(
+                leading: const Icon(Icons.coffee),
+                title: const Text('Buy us a coffee'),
+                subtitle: const Text('Support MeshMapper development'),
+                onTap: () => _launchUrl('https://buymeacoffee.com/meshmapper'),
+              ),
           ]),
 
           // Exit Options (Android only)