Fix: use backedBy 'user' for initial discourse nodes in block props

initSingleDiscourseNode was writing backedBy: "default" which caused
nodes to be filtered out of the settings panel when the flag is ON.
Also fixes up existing graphs that already stored the wrong value.

Author: sid597

apps/roam/src/components/settings/utils/init.ts

@@ -147,10 +147,12 @@ const initSingleDiscourseNode = async (
       tag: node.tag || "",
       graphOverview: node.graphOverview ?? false,
       canvasSettings: node.canvasSettings || {},
-      backedBy: "default",
+      backedBy: "user",
     });
 
     setBlockProps(pageUid, nodeData, false);
+  } else if (existingProps && existingProps["backedBy"] === "default") {
+    setBlockProps(pageUid, { ...existingProps, backedBy: "user" }, false);
   }
 
   return { label: node.text, pageUid };