Add default color for new node types in settings menu (#887)

New node types created via "Add Node Type" were missing the color field,
causing the color circle to not render. Default to grey (#808080).

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: trangdoan982

apps/obsidian/src/components/NodeTypeSettings.tsx

@@ -365,6 +365,7 @@ const NodeTypeSettings = () => {
       format: "",
       template: "",
       tag: "",
+      color: "#808080",
       created: now,
       modified: now,
     };