Convert remaining ui/services to TS

[kriswest]

Is your feature request related to a problem? Please describe.
Nearly all of the ui was converted to TS, however there remain 4/5 ui services that are still implemented in JS:

• src/ui/services/auth.js
• src/ui/services/config.js
• src/ui/services/git-push.js
• src/ui/services/repo.js

Note the duplicated code to calculate the baseURL. Also note the fallback to location.origin which API_BASE doesn't do (yet, see #1228 (comment))

The following service was converted to TS already and can be used as a model:

• src/ui/services/user.ts

Describe the solution you'd like
Pure TS codebase