feat: add application preloader, identity roles, and resilient database initialization with automated seeding

src/NexusReader.UI.Shared/Layout/MainLayout.razor

@@ -11,18 +11,18 @@
 @inject NavigationManager NavigationManager
 @implements IDisposable
 
-<div class="app-container @_platformClass @(FocusMode.IsFocusModeActive ? "focus-mode-active" : "")">
-    <div class="reader-pane">
-        <main>
-            @Body
-        </main>
-        <ReaderFooter />
-    </div>
+<AuthorizeView>
+    <Authorized>
+        <div class="app-container @_platformClass @(FocusMode.IsFocusModeActive ? "focus-mode-active" : "")">
+            <div class="reader-pane">
+                <main>
+                    @Body
+                </main>
+                <ReaderFooter />
+            </div>
 
-    <div class="resizer" id="sidebar-resizer"></div>
+            <div class="resizer" id="sidebar-resizer"></div>
 
-    <AuthorizeView>
-        <Authorized>
             <div class="intelligence-sidebar">
                 <IntelligenceToolbar />
                 <div class="intelligence-content">
@@ -46,9 +46,18 @@
                     </div>
                 </div>
             </div>
-        </Authorized>
-    </AuthorizeView>
-</div>
+        </div>
+    </Authorized>
+    <Authorizing>
+        <div class="app-preloader">
+            <div class="preloader-spinner"></div>
+            <div class="preloader-text">Weryfikacja...</div>
+        </div>
+    </Authorizing>
+    <NotAuthorized>
+        @Body
+    </NotAuthorized>
+</AuthorizeView>
 
 <div id="blazor-error-ui" data-nosnippet>
     An unhandled error has occurred.