feat: runtime-editable string collections

[chohner]

@joschka this is what we looked at last Friday.

The idea is to replace our hard-coded Singletypes that effectively just represent string lookup (like AmtsgerichtCommon and the contained fields such as featureName)

This instead would add a CollectionType (prototype name Translations, up for discussion), which allows dynamic editing of translation groups and containing fields.

pros:

• Adding / editing translation groups & variables at runtime without re-deploy
• No more typing of each variable in the App
• Explicit lookup and fallback (if a variable wasn't found we could still show Amtsgericht.featureName)

cons:

• Less type safety (we can't "know" that Amtsgericht.featureName exists via zod validation)
• Potential of accidental deletion/editing