Fix missing features and improve code quality

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.

src/main/resources/messages.yml

@@ -39,10 +39,11 @@ spy:
   enabled: "&#04CADFШпион режим включен"
   disabled: "&#04CADFШпион режим выключен"
   format: "&#808080[SPY] {sender} → {receiver}: {message}"
+  chat-format: "&#808080[SPY] {type} {sender}: {message}"
 
 filter:
   blocked: "&#04CADFСообщение заблокировано (мат)"
-  warned: "&#04CADFПредупреждение: не используйте мат!"
+  warning: "&#04CADFПредупреждение: не используйте мат!"
 
 cooldown:
   wait: "&#04CADFПодождите {time} сек перед следующим сообщением"