feat: add configurable logging level for backend and Mini App

- Introduced a new `LOG_LEVEL` configuration option in the `.env.example` file to allow users to set the logging level (DEBUG, INFO, WARNING, ERROR).
- Updated the `Settings` class to include the `log_level` attribute, normalizing its value to ensure valid logging levels are used.
- Modified the logging setup in `run.py` to utilize the configured log level, enhancing flexibility in log management.
- Enhanced the Mini App to include the logging level in the JavaScript configuration, allowing for consistent logging behavior across the application.
- Added a new `logger.js` module for frontend logging, implementing level-based filtering and console delegation.
- Included unit tests for the new logger functionality to ensure proper behavior and level handling.

duty_teller/run.py

@@ -24,7 +24,7 @@ async def _resolve_bot_username(application) -> None:
 
 logging.basicConfig(
     format="%(asctime)s - %(name)s - %(levelname)s - %(message)s",
-    level=logging.INFO,
+    level=config.LOG_LEVEL,
 )
 logger = logging.getLogger(__name__)