[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/useGlobalLitegraph.ts

@@ -8,7 +8,7 @@ import {
   LGraphNode,
   LLink,
   LiteGraph
-} from '@comfyorg/litegraph'
+} from '@/lib/litegraph/src/litegraph'
 
 /**
  * Assign all properties of LiteGraph to window to make it backward compatible.