fix(mgmt): version-agnostic OpenAPI drift test + regenerate the 0.5.0 snapshot

The snapshot comparison now normalizes info.version on both sides and
compares structurally — a version bump alone can never invalidate the
checked-in spec again (the 0.5.0 release tripped on exactly this; the
API surface is what drift-control protects). Snapshot regenerated so
the docs-site copy shows the current version.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

api/openapi.json

@@ -10,7 +10,7 @@
       "name": "MIT OR Apache-2.0",
       "identifier": "MIT OR Apache-2.0"
     },
-    "version": "0.4.2"
+    "version": "0.5.0"
   },
   "paths": {
     "/api/v1/clients": {