Chore(Webapp): Use labels in external data instead of form data

[arnaudfnr]

Problem

Currently in the app, some categorical data comes with labels that we display as is in the website. Those labels come from the form data which, as discussed with Cathalijne, are subject to change depending on the project.

Therefore, it has been decided that the categorical labels which can change will be integrated to external data (see for_label.parquet in data catalog for forest data).

Context

Currently we use the function findCategoricalLabel to map categorical data to its labels, from style.json metadata.

We need to use the data from "for_label" file, and for that we need to use a backend endpoint that returns this data according to the project.