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.

webapp/js/auth.js

@@ -2,6 +2,8 @@
  * Telegram init data and access checks.
  */
 
+import { logger } from "./logger.js";
+
 /**
  * Get tgWebAppData value from hash when it contains unencoded & and =.
  * Value runs from tgWebAppData= until next &tgWebApp or end.
@@ -33,7 +35,10 @@ export function getInitData() {
   const hash = window.location.hash ? window.location.hash.slice(1) : "";
   if (hash) {
     const fromHash = getTgWebAppDataFromHash(hash);
-    if (fromHash) return fromHash;
+    if (fromHash) {
+      logger.debug("initData from hash");
+      return fromHash;
+    }
     const hashParams = new URLSearchParams(hash);
     const tgFromHash = hashParams.get("tgWebAppData");
     if (tgFromHash) return tgFromHash;
@@ -42,6 +47,7 @@ export function getInitData() {
     ? new URLSearchParams(window.location.search).get("tgWebAppData")
     : null;
   if (q) {
+    logger.debug("initData from query");
     return q;
   }
   return "";