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/java/com/loki/lochat/commands/ClearChatCommand.java

@@ -19,9 +19,9 @@ public class ClearChatCommand implements CommandExecutor {
 
     @Override
     public boolean onCommand(@NotNull CommandSender sender, @NotNull Command command, @NotNull String label, @NotNull String[] args) {
-        // Отправляем 100 пустых строк всем игрокам
+        // Отправляем пустые строки всем игрокам для очистки чата
         for (Player player : Bukkit.getOnlinePlayers()) {
-            for (int i = 0; i < 100; i++) {
+            for (int i = 0; i < com.loki.lochat.utils.Constants.CLEAR_CHAT_LINES; i++) {
                 player.sendMessage("");
             }