feat(canvas): 绘图工具 - 集成 Excalidraw 并支持后台切换默认引擎

web/package.json

@@ -13,6 +13,7 @@
     "dependencies": {
         "@ant-design/icons": "^6.3.2",
         "@codemirror/lang-json": "^6.0.2",
+        "@excalidraw/excalidraw": "0.18.1",
         "@ffmpeg/ffmpeg": "^0.12.15",
         "@ffmpeg/util": "^0.12.2",
         "@mediapipe/tasks-vision": "^0.10.35",