Tokens now carry a keyed hash of the account's security stamp, and every
authenticated request compares it with the stored stamp (cached for 60 s,
evicted in-process on change). A password reset or change, a deactivation
and a deletion all rotate or remove the stamp, so tokens issued before them
get 401. Tokens without the claim get 401 too.
Both hosts now apply the same Identity password rule: at least 6 characters
with one uppercase letter, one number and one special character. Change
password requires an authenticated caller, verifies the current password
before evaluating the new one, and reports a policy rejection separately
from a wrong current password.
