nodes: per-node netmiko_device_type (controller-only)

netmiko_device_type follows the CONTROLLER_ONLY_PROPERTIES pattern
(like console_auto_start): a node created from a template inherits the
template value, PUT /nodes can override it inside a topology, updates
never round-trip to the compute, and the value persists in the project
topology file.

gns3server/schemas/controller/nodes.py

@@ -116,6 +116,11 @@ class NodeBase(BaseModel):
     console_auto_start: Optional[bool] = Field(
         False, description="Automatically start the console when the node has started"
     )
+    netmiko_device_type: Optional[str] = Field(
+        None,
+        description="Device type for Netmiko-based automation tools, overrides the template value",
+        pattern=r"^[a-z0-9_]+$",
+    )
     aux: Optional[int] = Field(None, gt=0, le=65535, description="Auxiliary console TCP port")
     aux_type: Optional[ConsoleType] = None
     properties: Optional[dict] = Field(default_factory=dict, description="Properties specific to an emulator")