Restore Python 3 type hints and f-strings in utils.py

- Add type hints to create_progress_bar() and format_stat_bar()
- Add type hints to admin_only() decorator and is_admin()
- Use f-strings for logging (Python 3.11 compatible)
- Improves code readability and IDE support

bot/utils.py

@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 """
 Utility functions and decorators for the bot.
 """