chore(deps): bump zod-openapi from 5.4.6 to 6.0.0

The v6 major leaves the createDocument API and the .meta() registry
annotations unchanged for this codebase; the generated
docs/api/openapi.yaml stays byte-identical and openapi:check passes
with no registry adjustment.

package.json

@@ -90,7 +90,7 @@
     "web-push": "^3.6.7",
     "yaml": "^2.8.4",
     "zod": "^4.4.3",
-    "zod-openapi": "^5.4.6",
+    "zod-openapi": "^6.0.0",
     "zxcvbn-typescript": "^5.0.1"
   },
   "devDependencies": {