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/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.