Update banned users handling with async support and improved date parsing

- Modified `change_page` function in `callback_handlers.py` to use async methods for retrieving banned users and their buttons.
- Enhanced `get_banned_users_list` in `helper_func.py` to handle string timestamps and various date formats, ensuring robust date parsing.
- Added a new test case in `test_utils.py` to validate the handling of string timestamps in the banned users list retrieval.

tests/test_utils.py

@@ -599,6 +599,24 @@ class TestUtilityFunctions:
         assert "Spam" in result
         assert "Violation" in result
     
+    @pytest.mark.asyncio
+    async def test_get_banned_users_list_with_string_timestamp(self):
+        """Тест получения списка заблокированных пользователей со строковым timestamp"""
+        mock_db = AsyncMock()
+        mock_db.get_banned_users_from_db_with_limits.return_value = [
+            (123, "Spam", "1704067200"),  # user_id, ban_reason, unban_date (string timestamp)
+            (456, "Violation", "1704153600")
+        ]
+        mock_db.get_username.return_value = None
+        mock_db.get_full_name_by_id.return_value = "Test User"
+        
+        result = await get_banned_users_list(0, mock_db)
+        
+        assert "Список заблокированных пользователей:" in result
+        assert "Test User" in result
+        assert "Spam" in result
+        assert "Violation" in result
+    
     @pytest.mark.asyncio
     async def test_get_banned_users_buttons(self):
         """Тест получения кнопок заблокированных пользователей"""