Node settings arrive as keyword arguments, not a params dict

A python node's settings are constants of its own function, so they are passed
the way its ports are: by name. The controller binds them to the compiled
function, the `params` field is gone from the worker and remote protocols, and
a setting sharing a port's name is reported as a node error rather than
shadowing it. The panel's scaffold follows suit and keeps the header in step
with both ports and settings.

The demo's `pace` moves from a flow input to a setting of the training node,
which is what it always was.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NUb8YpL2s3gmN9WTACTt4q

backend/tests/api/routes/test_flows.py

@@ -5,12 +5,12 @@ from app.core.config import settings
 PREFIX = f"{settings.API_V1_STR}/flows"
 
 WORKING_NODE = """
-def process(params):
+def process():
     return {"reading": 21.5}
 """
 
 BROKEN_NODE = """
-def process(params):
+def process():
     raise RuntimeError("boom")
 """
 
@@ -75,7 +75,7 @@ def test_broken_node_is_reported_and_siblings_stay_active(
     response = client.put(
         f"{PREFIX}/demo/nodes/logger/source",
         headers=superuser_token_headers,
-        json={"code": "def process(reading, params:\n"},
+        json={"code": "def process(reading:\n"},
     )
     assert response.status_code == 200
     assert response.json()["status"] == "error"
@@ -98,7 +98,7 @@ def test_running_a_flow_produces_values(
     client.put(
         f"{PREFIX}/demo/nodes/logger/source",
         headers=superuser_token_headers,
-        json={"code": "def process(reading, params):\n    return {}\n"},
+        json={"code": "def process(reading):\n    return {}\n"},
     )
 
     response = client.post(