[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/useNodeDragAndDrop.ts

@@ -1,4 +1,4 @@
-import type { LGraphNode } from '@comfyorg/litegraph'
+import type { LGraphNode } from '@/lib/litegraph/src/litegraph'
 
 type DragHandler = (e: DragEvent) => boolean
 type DropHandler<T> = (files: File[]) => Promise<T[]>