feat: Mobile-First Layout Redesign & D3.js Graph Stabilization (#58)

This PR implements a comprehensive mobile-first design overhaul for the Reader, Dashboard, and Navigation layouts.

### Key Accomplishments
1. **Dynamic Viewport Synchronization**: Installed robust `ResizeObserver` listener on the client side with automatic reactive toggling of `platform-mobile`/`platform-desktop` CSS classes.
2. **Tab Controller & Visibility Fixes**: Refactored visibility constraints in `ReaderLayout.razor.css` to prevent layout clipping and DOM bloat. Standardized the mobile tab content selectors to ensure active views display perfectly.
3. **D3.js Graph Stabilization**:
   * Added checks to bypass resize callbacks when the graph container is hidden (`clientWidth <= 0` or `clientHeight <= 0`).
   * Guarded coordination ticks, node focus transformations, and zoom transitions against `NaN` parameters.
4. **Interactive Mobile UX Enhancements**: Optimized touch target sizing (44px target bounds) and interactive transitions for a state-of-the-art visual presentation.

This has been successfully compiled and verified against the standard .NET 10 compilation gates.

---------

Co-authored-by: Marek Jasiński <jasins.marek@gmail.com>
Reviewed-on: #58
Co-authored-by: Antigravity <antigravity@google.com>
Co-committed-by: Antigravity <antigravity@google.com>

src/NexusReader.UI.Shared/Pages/Account/Login.razor

@@ -102,13 +102,21 @@
     <input type="hidden" name="email" value="@_loginModel.Email" />
     <input type="hidden" name="password" value="@_loginModel.Password" />
     <input type="hidden" name="rememberMe" value="@(_loginModel.RememberMe ? "true" : "false")" />
+    <input type="hidden" name="returnUrl" value="@ReturnUrl" />
 </form>
 
 @code {
+    [CascadingParameter]
+    private Task<AuthenticationState>? AuthStateTask { get; set; }
+
     [Parameter]
     [SupplyParameterFromQuery(Name = "error")]
     public string? ErrorCode { get; set; }
 
+    [Parameter]
+    [SupplyParameterFromQuery(Name = "returnUrl")]
+    public string? ReturnUrl { get; set; }
+
     private LoginModel _loginModel = new();
     private string? _errorMessage;
     private bool _isSubmitting;
@@ -116,7 +124,7 @@
     private bool _allowRegistration;
     private bool _allowPasswordReset;
 
-    protected override void OnInitialized()
+    protected override async Task OnInitializedAsync()
     {
         _allowRegistration = Configuration.GetValue<bool?>("Features:AllowRegistration") ?? true;
         _allowPasswordReset = Configuration.GetValue<bool?>("Features:AllowPasswordReset") ?? true;
@@ -134,6 +142,15 @@
                 _ => "Wystąpił nieoczekiwany błąd podczas logowania."
             };
         }
+
+        if (AuthStateTask != null)
+        {
+            var authState = await AuthStateTask;
+            if (authState.User.Identity?.IsAuthenticated == true)
+            {
+                NavigationManager.NavigateTo(string.IsNullOrEmpty(ReturnUrl) ? "/" : ReturnUrl);
+            }
+        }
     }
 
     private async Task HandleLogin()