refactor(app): split dashboard settings and layout into partial classes

src/Duempelkas.App/Components/Layout/MainLayout.razor

@@ -1,5 +1,4 @@
 @inherits LayoutComponentBase
-@using System.Reflection
 
 <div class="d-flex flex-column vh-100">
     <nav class="app-navbar d-flex justify-content-between align-items-center">
@@ -33,28 +32,3 @@
     </div>
 }
 
-@code {
-    private bool showAboutDialog;
-
-    private void OpenAboutDialog() => showAboutDialog = true;
-
-    private void CloseAboutDialog() => showAboutDialog = false;
-
-    private static string AppVersion
-    {
-        get
-        {
-            var entryAssembly = Assembly.GetEntryAssembly();
-            var infoVersion = entryAssembly?
-                .GetCustomAttribute<AssemblyInformationalVersionAttribute>()?
-                .InformationalVersion;
-
-            if (!string.IsNullOrWhiteSpace(infoVersion))
-            {
-                return infoVersion.Split('+')[0];
-            }
-
-            return entryAssembly?.GetName().Version?.ToString(2) ?? "1.0";
-        }
-    }
-}