fix(tests): suppress ink_sparkle shader crash in crash screen and about screen

CrashScreen creates its own MaterialApp which was loading InkSparkle
on first tap. Also fixes about_screen_test._buildScreen to use a
themed MaterialApp with NoSplash.

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

lib/ui/screens/crash_screen.dart

@@ -57,6 +57,7 @@ class CrashScreen extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     return MaterialApp(
+      theme: ThemeData(splashFactory: NoSplash.splashFactory),
       home: Scaffold(
         appBar: AppBar(
           title: const Text('Something went wrong'),

test/widget/about_screen_test.dart

@@ -50,7 +50,10 @@ Widget _buildScreen({List<Account> accounts = const []}) {
         FakeAccountRepository(accounts),
       ),
     ],
-    child: const MaterialApp(home: AboutScreen()),
+    child: MaterialApp(
+      theme: ThemeData(splashFactory: NoSplash.splashFactory),
+      home: const AboutScreen(),
+    ),
   );
 }