feat: implement epub service, navigation service, and global error boundary with updated reader UI layouts

src/NexusReader.Web.Client/Services/WasmEpubService.cs

@@ -0,0 +1,38 @@
+using System.Net.Http.Json;
+using FluentResults;
+using NexusReader.Application.Abstractions.Services;
+using NexusReader.Application.Queries.Reader;
+
+namespace NexusReader.Web.Client.Services;
+
+public class WasmEpubService : IEpubService
+{
+    private readonly HttpClient _httpClient;
+
+    public WasmEpubService(HttpClient httpClient)
+    {
+        _httpClient = httpClient;
+    }
+
+    public async Task<Result<ReaderPageViewModel>> GetEpubContentAsync(int chapterIndex)
+    {
+        try
+        {
+            var response = await _httpClient.GetAsync($"/api/epub/{chapterIndex}");
+            if (response.IsSuccessStatusCode)
+            {
+                var viewModel = await response.Content.ReadFromJsonAsync<ReaderPageViewModel>();
+                return viewModel != null ? Result.Ok(viewModel) : Result.Fail("Failed to deserialize response.");
+            }
+            
+            // Try to read the error message from the body
+            var errorBody = await response.Content.ReadAsStringAsync();
+            return Result.Fail($"Server error ({response.StatusCode}): {errorBody}");
+        }
+        catch (Exception ex)
+        {
+            // Fallback for network errors or parsing exceptions
+            return Result.Fail(new Error($"Network or parsing error: {ex.Message}").CausedBy(ex));
+        }
+    }
+}