Features fixed:
- Added chat filter functionality (block/warn/censor modes)
- Fixed spy command to monitor all chat messages
- Added proper spy notifications for global/local chat
Code quality improvements:
- Created PlayerUtil to eliminate code duplication in player lookup
- Refactored ChatListener into smaller, focused methods
- Added Constants class to replace magic numbers
- Improved SOLID principles compliance
- Fixed all compilation warnings
All features from README are now implemented and working.
