fix: EA-1 refuse authorize of an already-recorded key (v0.1.3)

authorize never checked the target fingerprint against existing docs before
save()'s upsert-by-_id, so authorizing the local machine's own public key
under a new friendly name silently replaced the local authorizer record
(can_authorize demoted to False) while printing a success banner. With a
sole authorizer this bricks the CLI: authorize refuses (not permitted),
init refuses (already initialized), and revoke of the local key refuses
(refusing to revoke the local key) -- no in-CLI recovery. Mirror revoke's
local-key guard and extend it to any existing _id, so a duplicate target
is refused with a clear message instead of silently replacing the record.

Signed-off-by: disqualifier <dev@disqualifier.me>

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "envelope_authorizer"
-version = "0.1.2"
+version = "0.1.3"
 description = "CLI key-authorization manager for envelope_crypto"
 requires-python = ">=3.10"
 dependencies = [