refactor: streamline MCP service handling and improve IPC registration

* Refactored MCPService to implement a singleton pattern for better instance management.
* Updated IPC registration to utilize the new getMcpInstance method for handling MCP-related requests.
* Removed redundant IPC handlers from the main index file and centralized them in the ipc module.
* Added background throttling option in WindowService configuration to enhance performance.
* Introduced delays in MCPToolsButton to optimize resource and prompt fetching after initial load.

src/main/services/WindowService.ts

@@ -446,7 +446,8 @@ export class WindowService {
         preload: join(__dirname, '../preload/index.js'),
         sandbox: false,
         webSecurity: false,
-        webviewTag: true
+        webviewTag: true,
+        backgroundThrottling: false
       }
     })