fix: repair imports lost in the 3.1 rebase and meet the new lint baseline

The rebase onto upstream 3.1 (mypy + ruff I001/F401 waves) left the tree
short of the newly enforced baselines in three ways:

* contextlib / UbridgeError imports dropped as false duplicates during
  conflict resolution left NameErrors in iou_vm and qemu_vm (F821);
  the Dynamips router grabbed the compute-level NIOTAP instead of the
  hypervisor one, breaking TAP anchoring (test failure).
* unused imports (KERNEL_UNSUPPORTED_FILTERS, UbridgeError, List) and
  unsorted blocks left behind where the stack's later commits moved the
  last usage elsewhere — ruff I001/F401/RUF022 now enforce these.
* mypy, now baseline-free: cache dict annotations in tc_probe, the
  locators candidate list, the resolved-params None branch in the MCP
  runner, and validate_bpf_syntax keeps the upstream Dict[str, Any]
  return (the strict Optional[str] was wrong for the "valid" bool entry).

The e2e raw-frame probe resolves its compiler via shutil.which (S607)
and zips with strict= (B905); the remaining subprocess call is S603 by
nature and gets a per-file ignore like other test files.

ruff check/format clean, mypy at upstream parity (no new errors),
full unit suite 2167 passed.

gns3server/api/routes/compute/capabilities.py

@@ -28,8 +28,8 @@ from gns3server.compute import MODULES
 from gns3server.compute.ubridge.tc_probe import (
     probe_bridge_tap_support,
     probe_iol_tap_support,
-    probe_tc_capabilities,
     probe_tap_support,
+    probe_tc_capabilities,
 )
 from gns3server.utils.path import get_default_project_directory
 from gns3server.utils.tc_capabilities import usable_ebpf_modes

gns3server/api/routes/compute/docker_nodes.py

@@ -264,8 +264,10 @@ async def duplicate_docker_node(
     dependencies=[Depends(compute_authentication)],
 )
 async def create_docker_node_nio(
-    adapter_number: int, port_number: int, nio_data: Union[schemas.UDPNIO, schemas.BridgeNIO],
-    node: DockerVM = Depends(dep_node)
+    adapter_number: int,
+    port_number: int,
+    nio_data: Union[schemas.UDPNIO, schemas.BridgeNIO],
+    node: DockerVM = Depends(dep_node),
 ) -> Union[schemas.UDPNIO, schemas.BridgeNIO]:
     """
     Add a NIO (Network Input/Output) to the node.
@@ -284,8 +286,10 @@ async def create_docker_node_nio(
     dependencies=[Depends(compute_authentication)],
 )
 async def update_docker_node_nio(
-    adapter_number: int, port_number: int, nio_data: Union[schemas.UDPNIO, schemas.BridgeNIO],
-    node: DockerVM = Depends(dep_node)
+    adapter_number: int,
+    port_number: int,
+    nio_data: Union[schemas.UDPNIO, schemas.BridgeNIO],
+    node: DockerVM = Depends(dep_node),
 ) -> Union[schemas.UDPNIO, schemas.BridgeNIO]:
     """
     Update a NIO (Network Input/Output) on the node.

gns3server/api/routes/compute/ethernet_switch_nodes.py

@@ -103,20 +103,20 @@ async def update_ethernet_switch(
     Update an Ethernet switch.
     """
 
-    node_data = jsonable_encoder(node_data, exclude_unset=True)
-    if "name" in node_data and node.name != node_data["name"]:
-        node.name = node_data["name"]
-    if "usage" in node_data:
-        node.usage = node_data["usage"]
-    if "ports_mapping" in node_data:
+    data = jsonable_encoder(node_data, exclude_unset=True)
+    if "name" in data and node.name != data["name"]:
+        node.name = data["name"]
+    if "usage" in data:
+        node.usage = data["usage"]
+    if "ports_mapping" in data:
         # capture the mapping before the setter replaces it: the VLAN
         # reconcile diffs old against new to touch only what changed, in
         # place (the setter itself keeps the port-count guard)
         previous_mapping = [dict(port) for port in node.ports_mapping]
-        node.ports_mapping = node_data["ports_mapping"]
+        node.ports_mapping = data["ports_mapping"]
         await node.update_port_settings(previous_mapping)
-    if "console_type" in node_data:
-        node.console_type = node_data["console_type"]
+    if "console_type" in data:
+        node.console_type = data["console_type"]
     node.updated()
     return node.asdict()