Custem centerLocation

### Description

Det ser ut som at man bare kan sette centerLocation til et bestemt punkt ved å skrive inn number i latitude/longitude.

Vi ønsker å kunne sette centerLocation basert på svar tidligere i skjema, da gjennom å referere til variabler i datamodellen.

### Additional Information

_No response_

Start by locating the existing centerLocation handling in the app-frontend-react codebase and trace how latitude and longitude values are read from configuration. Determine how earlier form answers are represented in the data model, then define completion as allowing centerLocation to resolve its coordinates from those variables rather than only fixed numbers.

Written by the indexing model from the issue text.