some fixes around processing server settings

[haraldschilly]

Description

1. process the string value using the to_val function right when the data comes in from the DB
2. the above means it is no longer necessary in the frontend
3. fix/enhance typing
4. I also noticed errors in "static", where the local source files are in ./src. I added them.
5. … and when I edited the tsconfig file, it also complaint about not setting the module resolution ordering, i.e. if "resolveJsonModule": true → I set moduleResolution": "node". More background about that in the moduleResolution documentation. If this setting introduces problems, which I hope it doesn't, we should definitely fix them and not revert the setting.

Checklist:

• [ ] Testing instructions are provided, if not obvious
• [ ] Release instructions are provided, if not obvious