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/Services/TrafficResetService.php

@@ -274,7 +274,7 @@ class TrafficResetService
   /**
    * Batch check and reset users. Processes all eligible users in batches.
    */
-  public function batchCheckReset(int $batchSize = 100, callable $progressCallback = null): array
+  public function batchCheckReset(int $batchSize = 100, ?callable $progressCallback = null): array
   {
     $startTime = microtime(true);
     $totalResetCount = 0;