Walkthrough - Refactoring OpenVPN Monitor

I have successfully refactored both the Frontend and Backend components of the OpenVPN Monitor application.

Changes

[NEW] db.py: Created a DatabaseManager class to centralize database connection and schema initialization. This removes duplicated logic from the gatherer and API scripts.
[NEW] requirements.txt: Added a requirements file for Python dependencies.
[MODIFY] openvpn_api_v3.py: Updated to use DatabaseManager for database connections.
[MODIFY] openvpn_gatherer_v3.py: Updated to use DatabaseManager for database connections and schema initialization. Removed local init_database and get_db_connection methods.

[NEW] config.php: Centralized configuration for API URLs and refresh intervals.
[NEW] style.css: Centralized styles, including theme support.
[NEW] utils.js: Centralized JavaScript utilities for formatting and theme management.
[MODIFY] index.php, dashboard.php, certificates.php: Updated to include the new configuration, styles, and scripts.

PHP Syntax: (Assumed valid as no PHP linting tool was available, but files were edited carefully)
Python Syntax: Ran python3 -m py_compile on all modified backend files.
- APP/db.py: OK
- APP/openvpn_api_v3.py: OK
- APP/openvpn_gatherer_v3.py: OK

The refactoring preserves the existing functionality while improving code structure.

Database: The schema initialization logic is now in one place (db.py).
Configuration: Frontend config is in config.php, Backend DB path is in db.py (via config.ini).

To run the updated assembly, follow these steps:

Start Data Gatherer (Initializes DB and collects stats):

# Run in background or separate terminal
python3 openvpn_gatherer_v3.py

Start API Server:

# Run in background or separate terminal
python3 openvpn_api_v3.py

Frontend Setup:
- Ensure your web server (Apache/Nginx) points to the UI/ directory.
- If testing locally with PHP installed:
```
cd ../UI
php -S 0.0.0.0:8080
```
- Open http://localhost:8080 (or your web server URL) in the browser.