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.

tests/test_app.py

@@ -35,7 +35,9 @@ def test_app_static_has_no_store_and_vary(client):
     r = client.get("/app/")
     if r.status_code != 200:
         r = client.get("/app")
-    assert r.status_code == 200, "webapp static mount should serve index at /app or /app/"
+    assert r.status_code == 200, (
+        "webapp static mount should serve index at /app or /app/"
+    )
     assert r.headers.get("cache-control") == "no-store"
     assert "accept-language" in r.headers.get("vary", "").lower()