feat: register telepath ObjectId adapter in project template

Wagtail's sidebar serializes page IDs via telepath, which has no
built-in handler for MongoDB ObjectId. This adds wagtail_hooks.py to
the project template that overrides build_node to delegate to
telepath's string primitive handler, fixing the UnpackableTypeError
at /cms/ on first load.

Author: aclark4life

src/dbx_python_cli/templates/project_template/project_name/wagtail_hooks.py

@@ -0,0 +1,12 @@
+from bson import ObjectId
+from telepath import Adapter, register
+
+
+class ObjectIdAdapter(Adapter):
+    """Serialize MongoDB ObjectId as its hex string for telepath/JS."""
+
+    def build_node(self, obj, context):
+        return context.build_node(str(obj))
+
+
+register(ObjectIdAdapter(), ObjectId)