Feat: Implement standalone offline activation mode via embedded server

Introduced a fully self-contained activation workflow (offline_activator.py) that eliminates the dependency on an external PHP backend. This allows the tool to function entirely on the local machine without internet access or a web server.

Key Implementation Details:
* Core Logic Port: Translated the PayloadGenerator logic and SQL template injection from PHP to Python, enabling dynamic SQLite database generation directly within the client script.
* Embedded Networking: Implemented LocalServer class using Python's http.server and socket modules to spawn a background HTTP listener on the local LAN interface.
* Dynamic Configuration: The script now resolves the local machine's IP address automatically to inject into the activation payloads, ensuring the device calls back to the host machine.
* Asset Handling: Device configuration files (MobileGestalt.plist) are now read directly from the local assets/Maker directory rather than being fetched remotely.
* Database Templates: Embedded SQL structures for BLDatabase and Downloads directly into the script constants to reduce file I/O and external dependencies.

Documentation:
* Added README_OFFLINE.md detailing the specific prerequisites and network requirements for the offline method.