dev.knotless.updateProfile

Changes the dev.knotless.profile record of the account logged in to this appview's web pages, as `knotless account profile` does: a field left out stays as it is, and one given empty is taken out, so the Bluesky profile's shows again. A profile left with nothing in it is deleted. Requires the session cookie the pages' login sets: the appview writes with the session it keeps for that account. Clients holding their own session write the record themselves.