refactor: 移除未使用的依赖和功能，优化代码结构

移除sharp模块及相关缩略图功能
删除webpack配置文件和安装脚本
清理未使用的依赖项
重构PHP服务端代码，优化缓存处理逻辑

package.json

@@ -1,15 +1,5 @@
 {
   "dependencies": {
-    "javascript-obfuscator": "^4.1.1",
-    "sharp": "^0.34.2"
-  },
-  "devDependencies": {
-    "webpack": "^5.99.9",
-    "webpack-cli": "^4.10.0",
-    "webpack-obfuscator": "^3.5.1"
-  },
-  "scripts": {
-    "build": "webpack",
-    "start": "node index.js"
+    "javascript-obfuscator": "^4.1.1"
   }
 }