Let a function node's own settings be edited

A python node's params reach process() as whatever its author put there,
but there was no way to put anything there: the settings form is built
from a type's declared schema, and a function node declares none.

Node types now say whether they take settings beyond their schema, and
the panel offers a key/value editor for the ones that do — named, typed
as text, number, on/off or JSON, and laid out like the port list beside
it. Rows are keyed by position rather than by name, so renaming a setting
does not remount the row and lose what was being typed into it.

Verified in the running app in both themes.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011LF61rxW1FG5YCD2J9YqjY

backend/app/flow/controller.py

@@ -101,6 +101,7 @@ class NodeType:
     # Constructor signatures differ per node type.
     cls: Any
     has_source: bool = False
+    free_params: bool = False
     params_schema: dict[str, Any] = field(default_factory=dict)
     #: Which installed package supplied this type, for the ones that are not
     #: built in.
@@ -118,6 +119,7 @@ NODE_TYPES: dict[str, NodeType] = {
         description="Your own Python code, run on every incoming message.",
         cls=Node,
         has_source=True,
+        free_params=True,
     ),
     "mqtt": NodeType(
         title="MQTT",
@@ -214,6 +216,7 @@ def node_type_info() -> list[NodeTypeInfo]:
             description=spec.description,
             params_schema=spec.params_schema,
             has_source=spec.has_source,
+            free_params=spec.free_params,
             plugin=spec.plugin,
         )
         for key, spec in NODE_TYPES.items()

backend/app/flow/schemas.py

@@ -155,5 +155,9 @@ class NodeTypeInfo(BaseModel):
     description: str
     params_schema: dict[str, Any] = Field(default_factory=dict)
     has_source: bool = False
+    #: Whether this type takes settings beyond the ones its schema declares.
+    #: A function node's params are its author's to name, and reach `process`
+    #: as whatever they put there.
+    free_params: bool = False
     #: The package a connector came from; empty for the built-in types.
     plugin: str | None = None