feat(widget): Widget 配置、loader 与右下角悬浮入口

生成可嵌入站点的 loader 与悬浮按钮，支持展开收起和移动端；附独立宿主测试页。

replypier-test/package.json

@@ -0,0 +1,12 @@
+{
+  "name": "replypier-test",
+  "version": "1.0.0",
+  "type": "module",
+  "scripts": {
+    "start": "node server.js"
+  },
+  "dependencies": {
+    "cors": "^2.8.5",
+    "express": "^5.2.1"
+  }
+}