[refactor] Migrate litegraph imports from npm package to local subtree

- Updated all imports from '@comfyorg/litegraph' to '@/lib/litegraph/src/'
- Replaced deep dist imports with direct source paths
- Updated CSS import in main.ts
- All imports now use the @ alias consistently

src/composables/node/useNodeCanvasImagePreview.ts

@@ -1,6 +1,5 @@
-import type { LGraphNode } from '@comfyorg/litegraph'
-
 import { useImagePreviewWidget } from '@/composables/widgets/useImagePreviewWidget'
+import type { LGraphNode } from '@/lib/litegraph/src/litegraph'
 
 const CANVAS_IMAGE_PREVIEW_WIDGET = '$$canvas-image-preview'