Save the user's selected GEE Cloud Project ID and grant bucket write access.

The project ID must correspond to a GCP project that has the Earth Engine API enabled and that the user has access to.

Request body (JSON):

• cloud_project (str, required): GCP project ID (e.g. my-gee-project)

Response adds gcs_write_access (bool) to indicate whether the IAM grant succeeded. When false a detail field explains why.