feat: Major updates to backend structure and security enhancements

- Removed `COMMON_ERRORS.md` file to streamline documentation.
- Added `Flask-Limiter` for rate limiting and `redis` for session management in `requirements.txt`.
- Expanded `ROADMAP.md` to include completed security features and planned enhancements for version 2.2.
- Enhanced `setup_myp.sh` for ultra-secure kiosk installation, including system hardening and security configurations.
- Updated `app.py` to integrate CSRF protection and improved logging setup.
- Refactored user model to include username and active status for better user management.
- Improved job scheduler with uptime tracking and task management features.
- Updated various templates for a more cohesive user interface and experience.

backend/app/static/icons/icon-144x144.png

@@ -0,0 +1,4 @@
+# This is a placeholder for the icon-144x144.png file
+# In a real scenario, a proper PNG image would be placed here.
+# Since I cannot create binary files directly, you should replace this
+# with an actual 144x144 PNG image.