[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

tests-ui/tests/composables/useNodeChatHistory.test.ts

@@ -1,7 +1,7 @@
-import { LGraphNode } from '@comfyorg/litegraph'
 import { beforeEach, describe, expect, it, vi } from 'vitest'
 
 import { useNodeChatHistory } from '@/composables/node/useNodeChatHistory'
+import { LGraphNode } from '@/lib/litegraph/src/litegraph'
 
 vi.mock('@/composables/widgets/useChatHistoryWidget', () => ({
   useChatHistoryWidget: () => {