feat: ✨ add environment variable support for proxy authentication and geo-blocking

- Introduced `.env.example` for environment variable configuration.
- Updated `docker-compose.yml` to utilize environment variables for proxy settings.
- Implemented proxy authentication with Basic Auth and geo-blocking based on country codes.
- Added `GEO_FILTER.md` for documentation on geo-filtering configuration.
- Enhanced logging to indicate authentication status and blocked countries during proxy server startup.

.gitignore

@@ -25,6 +25,9 @@ config.json
 data/
 !data/.gitkeep
 
+# Environment variables
+.env
+
 # Temporary files
 *.tmp
 *.bak