Refactor codebase resolving warnings and remove self-package imports

lib/view/settings/about/about.dart

@@ -0,0 +1,20 @@
+
+import 'package:flutter/material.dart';
+
+class About extends StatelessWidget {
+  const About({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(
+        title: const Text("Über diese App"),
+      ),
+      body: const Card(
+        elevation: 1,
+        borderOnForeground: true,
+        child: Text("Marianum Fulda"),
+      ),
+    );
+  }
+}