feat(ui): implement premium mobile-first reader layout with three-tab bottom navigation and assistant FAB

src/NexusReader.UI.Shared/Components/Organisms/ReaderCanvas.razor

@@ -13,6 +13,8 @@
 @inject IReaderInteractionService InteractionService
 @inject ISyncService SyncService
 @inject AuthenticationStateProvider AuthStateProvider
+@inject IQuizStateService QuizService
+@inject IPlatformService PlatformService
 @inject ILogger<ReaderCanvas> Logger
 
 <div class="reader-canvas @(ThemeService.IsLightMode ? "theme-light" : "theme-dark")">
@@ -53,6 +55,17 @@
         BlockId="@_selectedBlockId" 
         Coordinates="@_selectionCoords"
         FullPageContent="@GetFullPageContent()" />
+
+    @if (_isMobile)
+    {
+        <button class="nexus-mobile-assistant-fab @(QuizService.HasNewQuiz ? "has-new-quiz" : "")" @onclick="HandleAssistantFabClick" aria-label="Asystent AI">
+            <NexusIcon Name="robot" Size="24" Class="neon-glow" />
+            @if (QuizService.HasNewQuiz)
+            {
+                <span class="fab-badge"></span>
+            }
+        </button>
+    }
 </div>
 
 @code {
@@ -68,17 +81,29 @@
     private ElementReference _containerRef;
     private bool _isInteractive;
     private string? _currentActiveBlockId;
+    private bool _isMobile = false;
 
     protected override async Task OnInitializedAsync()
     {
         await Coordinator.ClearAsync();
         ThemeService.OnThemeChanged += HandleUpdate;
         NavigationService.OnNavigationChanged += OnNavigationChanged;
+        QuizService.OnQuizUpdated += HandleUpdate;
 
         InteractionService.OnScrollToBlockRequested += HandleScrollRequested;
         InteractionService.OnHighlightBlockRequested += HandleHighlightRequested;
         InteractionService.OnTextSelected += HandleTextSelected;
         SyncService.OnProgressReceived += HandleSyncProgressReceived;
+
+        var context = PlatformService.GetDeviceContext();
+        if (context.IsSuccess)
+        {
+            _isMobile = context.Value.DeviceType switch
+            {
+                DeviceType.Phone or DeviceType.Tablet => true,
+                _ => false
+            };
+        }
     }
 
     protected override async Task OnParametersSetAsync()
@@ -286,10 +311,16 @@
 
     private Task HandleUpdate() => InvokeAsync(StateHasChanged);
 
+    private async Task HandleAssistantFabClick()
+    {
+        await InteractionService.RequestAssistant();
+    }
+
     public void Dispose()
     {
         ThemeService.OnThemeChanged -= HandleUpdate;
         NavigationService.OnNavigationChanged -= OnNavigationChanged;
+        QuizService.OnQuizUpdated -= HandleUpdate;
 
         InteractionService.OnScrollToBlockRequested -= HandleScrollRequested;
         InteractionService.OnHighlightBlockRequested -= HandleHighlightRequested;