Completely rework UI's Config page

[GyulyVGC]

Completely rework UI's Config page to support widget-based interactions instead of raw-toml interactions.

This will allow setting up Nullnet service meshes in a much easier way, but having this task an high estimated effort, and being it just cosmetic and not functional, we can postpone it for now.

[antoncxx]

I'd also like to expand the scope of this task: we should consider moving away from .toml files and migrating that configuration into the SQL database, since we already use it for user management.

[GyulyVGC]

Yep, absolutely agree.
However since this is a huge item it's probably better not to include in the upcoming v0.1.0 though.