fix(v2): enforce hardened M0 contracts

contracts/repository/v1/repository.schema.json

@@ -6,7 +6,11 @@
   "additionalProperties": false,
   "required": ["repository_id", "format_version", "digest_algorithm", "compression", "encryption", "created_at"],
   "properties": {
-    "repository_id": {"type": "string", "format": "uuid"},
+    "repository_id": {
+      "type": "string",
+      "format": "uuid",
+      "pattern": "^[0-9a-f]{8}-[0-9a-f]{4}-7[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$"
+    },
     "format_version": {"const": 1},
     "digest_algorithm": {"const": "sha256"},
     "compression": {"enum": ["none", "zstd"]},
@@ -19,6 +23,6 @@
         "key_id": {"type": ["string", "null"], "minLength": 1}
       }
     },
-    "created_at": {"type": "string", "format": "date-time"}
+    "created_at": {"type": "string", "format": "date-time", "pattern": "^[0-9]{4}-[0-9]{2}-[0-9]{2}T[0-9]{2}:[0-9]{2}:[0-9]{2}(?:\\.[0-9]+)?Z$"}
   }
 }