Fix: Save complete app state (#40)

* pass rest of appState in put request

* fix: support both legacy and current currentItemRoundness formats

Add union type to accept both the old object format {type, value} and
the new enum format for backwards compatibility with existing drawings.

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Co-authored-by: Zimeng Xiong <zxzimeng@gmail.com>

frontend/src/pages/Editor.tsx

@@ -301,6 +301,7 @@ export const Editor: React.FC = () => {
 
     try {
       const persistableAppState = {
+        ...appState,
         viewBackgroundColor: appState?.viewBackgroundColor || '#ffffff',
         gridSize: appState?.gridSize || null,
       };