feat: enhance canvas functionality with new node types and improved data handling

- Added support for a new "compare" node type to facilitate side-by-side image comparisons.
- Updated AI image and prompt nodes to include aspect ratio handling for better image generation.
- Enhanced canvas toolbar to include export functionality for canvas data.
- Improved data resolution for compare nodes by resolving incoming edges and updating node data accordingly.
- Refactored frame node to support dynamic resizing and exporting capabilities.
- Introduced debounced saving for prompt node to optimize performance during user input.

app/globals.css

@@ -142,4 +142,11 @@
   .animate-shimmer {
     animation: shimmer 1.5s ease-in-out infinite;
   }
+}
+
+@layer components {
+  /* Verbindungs-Punkte über Node-Inhalt (XYFlow setzt kein z-index) */
+  .react-flow__handle {
+    z-index: 50;
+  }
 }