feat(ui/arch): Optimize Graph Dynamics, Immersive Reader, and Core Stability (#19)

This PR introduces a major optimization of graph dynamics, immersive reading experience, and architectural stabilization.

### 🚀 Key Improvements

- **Knowledge Graph (Fix #16)**:
  - Implemented smooth D3.js transitions using the General Update Pattern.
  - Added "Neon Flash" entry animations and dynamic node dimming for better focus.
- **Immersive Reader (Fix #12)**:
  - Standardized centered layout (`max-width: 800px`) with **Merriweather** typography.
  - Optimized line-height and letter-spacing for premium readability.
- **Technical Code Blocks (Fix #20)**:
  - High-contrast dark containers for code snippets.
  - **JetBrains Mono** integration and neon-accented scrollbars.
- **Architectural Stabilization**:
  - Enforced a strict **'no async void'** policy in UI services using `Func<Task>`.
  - Resolved WASM runtime DI errors by implementing dummy service proxies for server-side dependencies.
  - Replaced generic 'Not Found' message with a branded Nexus preloader.

Fixes #7, Fixes #12, Fixes #16, Fixes #20.

Reviewed-on: #19
Co-authored-by: Marek Jasiński <jasins.marek@gmail.com>
Co-committed-by: Marek Jasiński <jasins.marek@gmail.com>

src/NexusReader.Infrastructure/Services/EpubService.cs

@@ -46,34 +46,35 @@ public class EpubService : IEpubService
                 return Result.Fail($"EPUB file at '{fullPath}' is not accessible or does not exist.");
             }
 
-            EpubBook book;
-            try 
-            {
-                book = await EpubReader.ReadBookAsync(fullPath);
-            }
-            catch (Exception ex)
-            {
-                return Result.Fail(new Error($"Failed to parse EPUB file. It might be corrupted or in use. Path: {fullPath}").CausedBy(ex));
-            }
-            var blocks = new List<ContentBlock>();
-            int totalWordCount = 0;
-            int blockCounter = 0;
+            using var bookRef = await EpubReader.OpenBookAsync(fullPath);
+            var readingOrder = bookRef.GetReadingOrder();
 
-            if (book.ReadingOrder == null || !book.ReadingOrder.Any())
+            if (readingOrder == null || !readingOrder.Any())
             {
                 return Result.Fail("The EPUB has no readable content files in ReadingOrder.");
             }
 
             // Ensure index is within bounds
-            if (chapterIndex < 0 || chapterIndex >= book.ReadingOrder.Count)
+            if (chapterIndex < 0 || chapterIndex >= readingOrder.Count)
             {
                 chapterIndex = 0; // Default to first chapter
             }
 
-            var chapter = book.ReadingOrder[chapterIndex];
-            var chapterTitle = chapter.FilePath ?? $"Chapter {chapterIndex + 1}";
+            var chapterRef = readingOrder[chapterIndex];
+            
+            // Try to find a better title from navigation (TOC)
+            var navigation = bookRef.GetNavigation();
+            var chapterTitle = FindTitleInNavigation(navigation, chapterRef.FilePath) 
+                               ?? Path.GetFileNameWithoutExtension(chapterRef.FilePath) 
+                               ?? $"Chapter {chapterIndex + 1}";
 
-            var paragraphs = ExtractParagraphs(chapter.Content);
+            var chapterContent = await chapterRef.ReadContentAsTextAsync();
+
+            var blocks = new List<ContentBlock>();
+            int totalWordCount = 0;
+            int blockCounter = 0;
+
+            var paragraphs = ExtractParagraphs(chapterContent);
             foreach (var p in paragraphs)
             {
                 var sanitizedContent = SanitizeParagraph(p);
@@ -99,7 +100,7 @@ public class EpubService : IEpubService
                 blocks.Add(CreateAiTrigger($"trigger-{blockCounter++}"));
             }
 
-            return Result.Ok(new ReaderPageViewModel(blocks, chapterIndex, book.ReadingOrder.Count, chapterTitle));
+            return Result.Ok(new ReaderPageViewModel(blocks, chapterIndex, readingOrder.Count, chapterTitle));
         }
         catch (Exception ex)
         {
@@ -162,4 +163,25 @@ public class EpubService : IEpubService
             new List<string> { "Podsumuj", "Generuj Quiz", "Pomiń" }
         );
     }
+
+    private string? FindTitleInNavigation(IEnumerable<EpubNavigationItemRef> navigation, string? filePath)
+    {
+        if (string.IsNullOrEmpty(filePath)) return null;
+        
+        var fileName = Path.GetFileName(filePath);
+
+        foreach (var item in navigation)
+        {
+            // Match by full path or just filename as fallback
+            if (item.Link?.ContentFilePath == filePath || item.Link?.ContentFilePath == fileName)
+                return item.Title;
+                
+            if (item.NestedItems != null && item.NestedItems.Any())
+            {
+                var childTitle = FindTitleInNavigation(item.NestedItems, filePath);
+                if (childTitle != null) return childTitle;
+            }
+        }
+        return null;
+    }
 }