The Online sidebar's "Your blacklist" section is editable now: typing a
tag appends it and each entry gets an x to remove it. Changes are written
straight to the e621 account (PATCH /users/{id}.json with
user[blacklisted_tags]); the store keeps the fetched profile for the id,
updates the list optimistically and reloads it from e621. The Followed
page's blacklist cloud is rebuilt afterwards via the new
/api/follows/cloud/?refresh=1 force flag.
Verified against the live API with a reversible add/verify/restore test.