fix(core): add null checks for timeout refs and event listeners for React 19 compatibility (#9116)

## Description
- Add null checks before clearTimeout calls in colorful-fallback.tsx, edgeless.dialog.tsx, and local.dialog.tsx
- Fix event listener cleanup in unfolding.tsx
- Update tsconfig.jsx to use react-jsx transform

## Testing
- [x] Verified type safety improvements for React 19 compatibility
- [x] Ensured proper cleanup of event listeners and timeouts
- [x] Confirmed no unintended side effects from the changes

Link to Devin run: https://app.devin.ai/sessions/2e790f3ea0d84402837ec6c3c6f83e4c

packages/frontend/admin/src/modules/layout.tsx

@@ -139,7 +139,9 @@ export function Layout({ children }: PropsWithChildren) {
                 {children}
               </ResizablePanel>
               <RightPanel
-                rightPanelRef={rightPanelRef}
+                rightPanelRef={
+                  rightPanelRef as RefObject<ImperativePanelHandle>
+                }
                 onExpand={handleExpand}
                 onCollapse={handleCollapse}
               />