Refactor: standardize namespace and using directive style

Refactored all C# test files to use explicit namespace declarations and moved all using directives inside the namespace block for consistency. Updated assembly info and cache files to reflect the new build. Adjusted MvcTestingAppManifest.json to use fully qualified assembly names. No functional changes; all updates are related to code style, organization, and project metadata.

MediaBrowser.Model/Playlists/PlaylistCreationRequest.cs

@@ -2,13 +2,13 @@
 // Copyright (c) PlaceholderCompany. All rights reserved.
 // </copyright>
 
-using System;
-using System.Collections.Generic;
+namespace MediaBrowser.Model.Playlists;
+
+using global::System;
+using global::System.Collections.Generic;
 using Jellyfin.Data.Enums;
 using MediaBrowser.Model.Entities;
 
-namespace MediaBrowser.Model.Playlists;
-
 /// <summary>
 /// A playlist creation request.
 /// </summary>

MediaBrowser.Model/Playlists/PlaylistCreationResult.cs

@@ -4,15 +4,17 @@
 
 #pragma warning disable CS1591
 
-namespace MediaBrowser.Model.Playlists
-{
-    public class PlaylistCreationResult
-    {
-        public PlaylistCreationResult(string id)
-        {
-            Id = id;
-        }
+namespace MediaBrowser.Model.Playlists;
+   public class PlaylistCreationResult
+   {
+       /// <summary>
+       /// Initializes a new instance of the <see cref="PlaylistCreationResult"/> class.
+       /// </summary>
+       /// <param name="id">The playlist identifier.</param>
+       public PlaylistCreationResult(string id)
+       {
+           Id = id;
+       }
 
-        public string Id { get; }
-    }
-}
+       public string Id { get; }
+   }

MediaBrowser.Model/Playlists/PlaylistUpdateRequest.cs

@@ -2,12 +2,12 @@
 // Copyright (c) PlaceholderCompany. All rights reserved.
 // </copyright>
 
-using System;
-using System.Collections.Generic;
-using MediaBrowser.Model.Entities;
-
 namespace MediaBrowser.Model.Playlists;
 
+using global::System;
+using global::System.Collections.Generic;
+using MediaBrowser.Model.Entities;
+
 /// <summary>
 /// A playlist update request.
 /// </summary>

MediaBrowser.Model/Playlists/PlaylistUserUpdateRequest.cs

@@ -2,10 +2,10 @@
 // Copyright (c) PlaceholderCompany. All rights reserved.
 // </copyright>
 
-using System;
-
 namespace MediaBrowser.Model.Playlists;
 
+using global::System;
+
 /// <summary>
 /// A playlist user update request.
 /// </summary>