[Feature] Add Quit Stash option from the Web UI

[skier233]

Is your feature request related to a problem? Please describe. I wasn't aware it was possible to quit stash other than through task manager until I asked and someone pointed out that it's possible with the windows task bar in the bottom right. I hardly ever use this toolbar because so few apps use it and the ones that do always allow you to perform the same functionality elsewhere. I think it makes sense to add this same functionality within the webapp as well for consistency so users like me that weren't aware of it's existence still have a way to close stash.

Describe the solution you'd like Adding an option to the UI (maybe right next to the log out button in the top right) to quit stash

Describe alternatives you've considered Currently just killing with task manager. This could cause to data corruption though.

Additional context