fix(marker): ride markers on NIO so they survive node restart and project reload

Mirror the packet-filter lifecycle: marker specs now live on the NIO
(next to filters), ride in link_data from controller to compute on
every NIO create/update, and are reapplied by _ubridge_apply_markers
in add_ubridge_udp_connection (bridge creation / node restart) and
update_ubridge_udp_connection (NIO update — following the preceding
reset_packet_filters so markers survive filter changes).

Changes:
- NIO / NIOUDP: _markers property + asdict
- schemas/compute/nios.py: UDPNIO.markers field
- base_manager.create_nio: nio.markers from settings
- PUT /nio routes (vpcs/qemu/docker): nio.markers update
- base_node: _ubridge_apply_markers(bridge_name, nio) iterates
  nio.markers, computes pcap path, calls _ubridge_add_marker_filter
  + MarkerManager.register; called after _ubridge_apply_filters
- controller udp_link: _get_node_markers + _markers_for_node (route
  by capture_node_id); markers in create() and update() link_data
- /markers/start,stop endpoints: mirror spec onto nio.markers so
  the marker survives a subsequent node stop/start without a PUT
- tests: add markers field to NIO data expectations

This covers:
- Node restart: NIO persists, add_ubridge_udp_connection re-applies
- Filter update: reset wipes markers, _ubridge_apply_markers re-adds
- Project reload: create() carries markers in link_data → create_nio
- Immediate create: endpoint sets nio.markers immediately

gns3server/api/routes/compute/docker_nodes.py

@@ -294,6 +294,7 @@ async def update_docker_node_nio(
     nio.filters.clear()
     if nio_data.filters:
         nio.filters = nio_data.filters
+    nio.markers = nio_data.markers or {}
     await node.adapter_update_nio_binding(adapter_number, nio)
     return nio.asdict()
 
@@ -378,6 +379,11 @@ async def start_docker_node_marker(
     MarkerManager.instance().register(
         str(project_id), node.id, marker_data.name, marker_data.link_id, marker_data.tag
     )
+    nio = node.get_nio(adapter_number)
+    if nio:
+        nio.markers[marker_data.name] = {
+            "bpf": marker_data.bpf, "tag": marker_data.tag, "link_id": marker_data.link_id
+        }
     return {"pcap_file_path": str(pcap_path)}
 
 
@@ -398,6 +404,9 @@ async def stop_docker_node_marker(
 
     await node.stop_marker(adapter_number, marker_data.name)
     MarkerManager.instance().unregister(node.id, marker_data.name)
+    nio = node.get_nio(adapter_number)
+    if nio:
+        nio.markers.pop(marker_data.name, None)
 
 
 @router.get(