Fix PDF mobile compatibility and resolve build script conflict

Author: html-proof

package.json

@@ -4,7 +4,7 @@
   "private": true,
   "scripts": {
     "dev": "next dev",
-    "build": "next build --webpack",
+    "build": "next build",
     "start": "next start",
     "lint": "eslint"
   },

src/components/public/FilePreviewModal.tsx

@@ -281,7 +281,7 @@ export default function FilePreviewModal({ file, onClose }: FilePreviewModalProp
 
                     {isPdf && (
                         <iframe
-                            src={file.fileUrl}
+                            src={`https://docs.google.com/viewer?url=${encodeURIComponent(file.fileUrl)}&embedded=true`}
                             style={{
                                 width: "100%",
                                 height: "100%",