Refactor the `Whoami` handler to validate token metadata (status, expiration,
revocation) against Redis before database lookup, ensuring consistency with
balancer logic. Add `allow_ips`, `deny_ips`, and `expires_at` fields to
authentication responses.
Update internal middleware to support explicit anonymous access configuration
and harden security for unconfigured tokens.
Remove legacy fallback logic for master keys without digests.
BREAKING CHANGE: Internal endpoints now reject requests by default if no stats token is configured. To allow unauthenticated access, set `internal.allow_anonymous` to true.
BREAKING CHANGE: Support for legacy master keys without stored digests has been removed.
