feat: add remote directory picker to file sync

[deansheather]

Adds a new remote directory picker window used when creating a file sync to select the remote directory.

NVIDIA_Overlay_LplyNOug3n.mp4

TODOs:

• Use a dropdown for picking workspace agent in the file sync UI, currently it's typed out (and will crash if empty lol)
• Fix reactivation of the window, try to make it function like any other system dialog window

Closes #27

[deansheather]

It's ready for review, just need to finish the few TODOs