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。

frontend/public/config.dev.js

@@ -0,0 +1,32 @@
+// Runtime configuration - this file gets replaced at container startup
+// Assigned to `self` so the service worker can importScripts() it too;
+// in a page self === window, so window.APP_CONFIG still works.
+self.APP_CONFIG = {
+    // API URLs
+    API_URL: "https://devapi.replypier.site/api/v1",
+    WS_URL: "wss://devapi.replypier.site",
+    WIDGET_URL: "https://devapp.replypier.site",
+    
+    // Firebase Configuration
+    FIREBASE_API_KEY: "AIzaSyDTwDgANnBItYx39qm-6shq4cUws6QY4wI",
+    FIREBASE_AUTH_DOMAIN: "replypier-13e0a.firebaseapp.com",
+    FIREBASE_PROJECT_ID: "replypier-13e0a",
+    FIREBASE_MESSAGING_SENDER_ID: "680125690355",
+    FIREBASE_APP_ID: "1:680125690355:web:466f50999a6c91935ae286",
+    FIREBASE_STORAGE_BUCKET: "replypier-13e0a.firebasestorage.app",
+    FIREBASE_MEASUREMENT_ID: "G-7LGB58R2Q7",
+    FIREBASE_VAPID_KEY: "BJKnggErez2qK3AxBhHyEV-EoS9lfcWO1GDXhRwUKIHbT_PH23vhY_8HRIz_KyuC-0gbuViSrtSMiFp7zgyYY4g",
+    
+    // Razorpay Checkout
+    RAZORPAY_KEY_ID: "rzp_test_T92OR9gqPBht0N",
+    GTM_ID: "",
+
+    // Google Fonts API
+    GOOGLE_FONTS_API_KEY: "AIzaSyCTQCSK_ybLEglabeusbyekQGEyvFr2C5o",
+    
+    DEMO_WIDGET_ID: "a6ee36e9-b70e-4b12-8f94-cc5a5b147f26",
+    // Node Environment
+    NODE_ENV: "development",
+    HOST: "0.0.0.0"
+  };
+