fix: frontend reading incorrect data folder

[dennisrijsdijk]

Description of the Change

When --fbuser-data-directory=/path/to/dataFolder is passed into Firebot, the backend correctly uses this directory. However, the frontend doesn't. Because of this, some things like the profile selector use data from appdata, while the backend uses the specified data path.

This PR passes the fbuser-data-folder parameter into the MainWindow to ensure both frontend and backend are always working on the same data folder.

Testing

Ensured the profiles overview shows the profiles for the specified data folder, rather than the appdata folder.