feat: plugin controller config system with guest_comm_config hook integration

- Add HasPluginConfig trait and PluginController base class
- Integrate guest_comm_config hook in CommController for plugin frontend config injection
- Add user creation functionality to UserService and fix null value handling
- Enhance AbstractPlugin.getConfig() with key parameter support
- Multiple service layer optimizations and architecture improvements

app/Http/Controllers/PluginController.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace App\Http\Controllers;
+
+use App\Traits\HasPluginConfig;
+
+/**
+ * 插件控制器基类
+ * 
+ * 为所有插件控制器提供通用功能
+ */
+abstract class PluginController extends Controller
+{
+  use HasPluginConfig;
+
+  /**
+   * 执行插件操作前的检查
+   */
+  protected function beforePluginAction(): ?array
+  {
+    return null;
+  }
+}