Bundle hub registration schema in the installed package

Load the schema from reuse_surface/hub/ next to store.py and declare
package-data so pip install includes the YAML in site-packages. Fixes
hub register 500 in the container image.

reuse_surface/hub/store.py

@@ -9,9 +9,7 @@ from typing import Any
 import yaml
 from jsonschema import Draft202012Validator
 
-from reuse_surface.registry import ROOT
-
-SCHEMA_PATH = ROOT / "schemas" / "hub-registration.schema.yaml"
+SCHEMA_PATH = Path(__file__).resolve().parent / "hub-registration.schema.yaml"
 
 
 def _utc_now() -> str: