refactor: 重构变量选择器组件

- 删除旧的 VariablePicker 组件
- 更新 package.json 依赖配置

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: xlorne

frontend/packages/flow-pc/flow-pc-design/src/components/design-editor/node-components/strategy/VariablePicker.module.less

@@ -23,10 +23,9 @@
     "react-dom": ">=18"
   },
   "dependencies": {
+    "@flow-engine/flow-core": "workspace:*",
     "@ant-design/icons": "~6.1.0",
     "antd": "^6.2.1"
   },
-  "devDependencies": {
-
-  }
-}
+  "devDependencies": {}
+}