marker: drop deleted marker from port NIO cache to stop empty pcap on restart

Deleting a marker while its node was stopped, then starting the node, recreated
an empty pcap. Root cause: delete_marker_capture removed the uBridge filter and
the pcap file but not the marker spec cached on the port NIO (nio.markers) —
the data source _ubridge_apply_markers reads on node start. The stale spec
reinstalled the marker when uBridge came up.

This was a regression from switching stop_marker off update() (which re-sent
the NIO and implicitly refreshed nio.markers) to the fine-grained
node.delete(/markers/{name}) path.

Fix: make the delete port-aware so the compute can locate the NIO. The DELETE
marker route becomes /adapters/{a}/ports/{p}/markers/{name} across all six
node types; the handler resolves the NIO via get_nio and passes it to
delete_marker_capture, which now pops the marker from nio.markers. get_nio
works regardless of uBridge state, so the stopped-node case is covered. The
controller's stop_marker targets the capture side's adapter/port.

gns3server/controller/udp_link.py

@@ -444,7 +444,10 @@ class UDPLink(Link):
             side = next((s for s in self._nodes if str(s["node"].id) == str(capture_node_id)), None)
             if side is not None:
                 try:
-                    await side["node"].delete(f"/markers/{name}", params={"link_id": self._id})
+                    await side["node"].delete(
+                        f"/adapters/{side['adapter_number']}/ports/{side['port_number']}/markers/{name}",
+                        params={"link_id": self._id},
+                    )
                 except Exception:
                     pass  # best-effort: old compute without the route leaves the file
         self._project.emit_notification("link.updated", self.asdict())