refactor(ui): fix layout issues and temporarily disable auth features

- app & navbar: comment out login, register, and logout features.
- scan-page: align info cards vertically and reduce upload area padding.
- mobile-nav: implement React Portal to fix overlapping menu issue.

apps/web/src/pages/scan-page.tsx

@@ -103,7 +103,7 @@ export function ScanPage() {
               {!previewUrl ? (
                 <div className="space-y-3">
                   <div
-                    className="w-full border-2 border-dashed border-green-300 rounded-md p-12 h-60 text-center cursor-pointer"
+                    className="w-full border-2 border-dashed border-green-300 rounded-md p-10 h-60 text-center cursor-pointer"
                     onClick={() => inputRef.current?.click()}
                   >
                     <Upload className="mx-auto text-green-500 mb-3" size={48} />