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- **Cleanup**: Removed obsolete interfaces and constants that were superseded by newer Application layer implementations.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>

src/NexusReader.Infrastructure.Mobile/Services/MauiStorageService.cs

@@ -6,66 +6,66 @@ namespace NexusReader.Infrastructure.Mobile.Services;
 
 public sealed class MauiStorageService : INativeStorageService
 {
-    public Result SaveString(string key, string value)
+    public Task<Result> SaveStringAsync(string key, string value)
     {
         try 
         {
             Preferences.Default.Set(key, value);
-            return Result.Ok();
+            return Task.FromResult(Result.Ok());
         }
         catch (Exception ex)
         {
-            return Result.Fail(ex.Message);
+            return Task.FromResult(Result.Fail(ex.Message));
         }
     }
 
-    public Result<string?> GetString(string key)
+    public Task<Result<string?>> GetStringAsync(string key)
     {
         try 
         {
-            return Result.Ok(Preferences.Default.Get(key, (string?)null));
+            return Task.FromResult(Result.Ok(Preferences.Default.Get(key, (string?)null)));
         }
         catch (Exception ex)
         {
-            return Result.Fail(ex.Message);
+            return Task.FromResult(Result.Fail<string?>(ex.Message));
         }
     }
 
-    public Result SaveBool(string key, bool value)
+    public Task<Result> SaveBoolAsync(string key, bool value)
     {
         try 
         {
             Preferences.Default.Set(key, value);
-            return Result.Ok();
+            return Task.FromResult(Result.Ok());
         }
         catch (Exception ex)
         {
-            return Result.Fail(ex.Message);
+            return Task.FromResult(Result.Fail(ex.Message));
         }
     }
 
-    public Result<bool> GetBool(string key, bool defaultValue = false)
+    public Task<Result<bool>> GetBoolAsync(string key, bool defaultValue = false)
     {
         try 
         {
-            return Result.Ok(Preferences.Default.Get(key, defaultValue));
+            return Task.FromResult(Result.Ok(Preferences.Default.Get(key, defaultValue)));
         }
         catch (Exception ex)
         {
-            return Result.Fail(ex.Message);
+            return Task.FromResult(Result.Fail<bool>(ex.Message));
         }
     }
 
-    public Result Remove(string key)
+    public Task<Result> RemoveAsync(string key)
     {
         try 
         {
             Preferences.Default.Remove(key);
-            return Result.Ok();
+            return Task.FromResult(Result.Ok());
         }
         catch (Exception ex)
         {
-            return Result.Fail(ex.Message);
+            return Task.FromResult(Result.Fail(ex.Message));
         }
     }
 
@@ -94,16 +94,16 @@ public sealed class MauiStorageService : INativeStorageService
         }
     }
 
-    public Result RemoveSecure(string key)
+    public Task<Result> RemoveSecureAsync(string key)
     {
         try
         {
             SecureStorage.Default.Remove(key);
-            return Result.Ok();
+            return Task.FromResult(Result.Ok());
         }
         catch (Exception ex)
         {
-            return Result.Fail(ex.Message);
+            return Task.FromResult(Result.Fail(ex.Message));
         }
     }
 }