refactor: 重命名SDK为iflow-engine，使用npm包引入第三方引擎

- 将包名从 @fishdingding/bim-engine-sdk 改为 iflow-engine
- 将构建输出文件从 bim-engine-sdk.*.js 改为 iflow-engine.*.js
- 将全局变量从 LyzBimEngineSDK 改为 IflowEngine
- 将第三方引擎SDK从本地引入改为npm包引入 (iflow-engine-base)
- 移除本地 src/engine_base 目录，移至回收站
- 更新所有文档和demo中的引用

demo/package.json

@@ -7,8 +7,8 @@
     "dev": "vite",
     "build": "vite build",
     "preview": "vite preview",
-    "copy-sdk": "mkdir -p lib && cp ../dist/bim-engine-sdk.umd.js lib/ && cp ../dist/bim-engine-sdk.umd.js.map lib/ 2>/dev/null || true",
-    "copy-draco": "mkdir -p static/js/draco && cp ../src/engine_base/draco/*.js ../src/engine_base/draco/*.wasm static/js/draco/ 2>/dev/null || true",
+    "copy-sdk": "mkdir -p lib && cp ../dist/iflow-engine.umd.js lib/ && cp ../dist/iflow-engine.umd.js.map lib/ 2>/dev/null || true",
+    "copy-draco": "mkdir -p static/js/draco && cp ../node_modules/iflow-engine-base/dist/draco/*.js ../node_modules/iflow-engine-base/dist/draco/*.wasm static/js/draco/ 2>/dev/null || true",
     "copy-all": "npm run copy-sdk && npm run copy-draco"
   },
   "devDependencies": {