fix(marker): validate marker name and expose enabled via REST

Add a name pattern constraint to MarkerCreate schema (alphanumeric +
_.-) to prevent injection into uBridge commands, with a matching
defense-in-depth check in _ubridge_add_marker_filter for hand-edited
topology files. Also add the missing "enabled" field to MarkerCreate
and pass it through the PUT route so the documented toggle actually
works.

gns3server/api/routes/controller/links.py

@@ -506,6 +506,7 @@ async def update_marker(
         bpf=marker_data.bpf if marker_data.bpf else None,
         tag=marker_data.tag,
         color=marker_data.color,
+        enabled=marker_data.enabled,
     )
     return link.markers.get(marker_name, {})