Refactor: Web Consolidation and Identity Stabilization (#40)

## Overview
This PR completes the architectural consolidation of the web project and stabilizes the Identity-based authentication flow for the NexusReader application. It also refines the UI aesthetic for the Book Ingestion Modal as requested in #33.

## Key Changes
- **Project Consolidation**: Fully merged `NexusReader.Web.New` into `NexusReader.Web`. This includes updating all namespace references, VS Code launch/task configurations, and CI/CD (`Dockerfile`).
- **Identity Stabilization**:
  - Implemented `IIdentityService` on the server using `SignInManager<NexusUser>` and `UserManager<NexusUser>`.
  - Fixed registration logic to include mandatory fields (`SubscriptionPlanId`, `TenantId`).
  - Updated `Login.razor` to force a page reload on successful login, ensuring proper synchronization of authentication cookies between SignalR and the browser.
- **UI/UX Refinement**:
  - Updated `BookIngestionModal` styling to follow the **Nexus Neon** design system.
  - Added premium button styles with hover effects and glows.
  - Improved modal layout and interaction feedback (shimmer effects, spinner colors).
- **Cleanup**: Removed obsolete interfaces and constants that were superseded by newer Application layer implementations.

## Verification
- Successfully built the solution: `dotnet build NexusReader.slnx --no-restore`
- Verified project structure and file moves.
- Validated server-side authentication logic.

Fixes #33

---------

Co-authored-by: Marek Jasiński <jasins.marek@gmail.com>
Reviewed-on: #40
Co-authored-by: Antigravity <antigravity@google.com>
Co-committed-by: Antigravity <antigravity@google.com>

tests/NexusReader.Application.Tests/NexusReader.Application.Tests.csproj

@@ -0,0 +1,19 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.11.1" />
+    <PackageReference Include="xunit" Version="2.9.0" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.8.2" />
+    <PackageReference Include="FluentAssertions" Version="6.12.0" />
+    <PackageReference Include="Moq" Version="4.20.70" />
+  </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\..\src\NexusReader.Application\NexusReader.Application.csproj" />
+    <ProjectReference Include="..\..\src\NexusReader.Infrastructure\NexusReader.Infrastructure.csproj" />
+  </ItemGroup>
+</Project>

tests/NexusReader.Application.Tests/Services/EpubMetadataExtractorTests.cs

@@ -0,0 +1,25 @@
+using System.IO;
+using System.Threading.Tasks;
+using FluentAssertions;
+using NexusReader.Infrastructure.Services;
+using Xunit;
+
+namespace NexusReader.Application.Tests.Services;
+
+public class EpubMetadataExtractorTests
+{
+    [Fact]
+    public async Task ExtractMetadataAsync_WithInvalidStream_ReturnsFailure()
+    {
+        // Arrange
+        var extractor = new EpubMetadataExtractor();
+        using var stream = new MemoryStream(new byte[] { 0, 1, 2, 3 });
+
+        // Act
+        var result = await extractor.ExtractMetadataAsync(stream);
+
+        // Assert
+        result.IsSuccess.Should().BeFalse();
+        result.Errors.Should().NotBeEmpty();
+    }
+}