Added all missing GUI-related messages to src/main/resources/message.yml for both ContractGUI and PlayerInventoryGUI.
Refactored ContractGUI.java to use the message manager for its navigation buttons.
Refactored the entire PlayerInventoryGUI.java to remove hardcoded strings and use the ConfigManager for all displayed text, making it consistent with the rest of the plugin.
Added a getRawMessage method to ConfigManager.java to safely retrieve raw string values for use in placeholders, which was necessary to fix a compilation error introduced during the refactoring.