Fixes:
- Fixed spam of join/quit messages when kicking non-whitelisted players
- Prevented join message from being sent before kicking unauthorized players
- Removed quit messages for players kicked by the whitelist system
Improvements:
- Optimized memory usage with HashSet for tracking kicked players
- Synchronized join/quit event handling for better performance
- Adjusted event priority to HIGHEST for reliable message cancellation
- NOTE: Recommended server restart after updating for full changes to take effect