Rename the trigger node type to debounce, migrating stored flows

The store rewrites `"type": "trigger"` to `debounce` in every published and
draft flow when it opens, bumps the version and commits once. No alias stays
behind, so `trigger` is now an unknown type.

backend/fluksio/flow/controller.py

@@ -40,6 +40,7 @@ from fluksio.flow.messages import MessageSpec, flow_of, qualify
 from fluksio.flow.nodes import (
     RESERVED_SETTINGS,
     ChangeNode,
+    DebounceNode,
     DelayNode,
     ExecNode,
     FileNode,
@@ -53,7 +54,6 @@ from fluksio.flow.nodes import (
     NtfyNode,
     RbeNode,
     SwitchNode,
-    TriggerNode,
     WebSocketNode,
     WrenNode,
 )
@@ -408,11 +408,11 @@ NODE_TYPES: dict[str, NodeType] = {
         cls=JoinNode,
         params_schema=_schema_of(JoinNode),
     ),
-    "trigger": NodeType(
-        title="Trigger",
+    "debounce": NodeType(
+        title="Debounce",
         description="Send one value now and another once things go quiet.",
-        cls=TriggerNode,
-        params_schema=_schema_of(TriggerNode),
+        cls=DebounceNode,
+        params_schema=_schema_of(DebounceNode),
     ),
     "exec": NodeType(
         title="Command",