fix(files): update qr code style

public/static/css/white.css

@@ -234,6 +234,13 @@
   backdrop-filter: blur(9.5px);
 }
 
+.theme-default .qrcode-flat {
+  padding: 1rem;
+  background-color: #ecf0f1;
+  display: inline-block;
+  background: rgba(255, 255, 255, 0.8);
+}
+
 .theme-default .qrcode-container {
   height: 3rem;
 }

src/client/web/src/components/panel_files.tsx

@@ -656,7 +656,7 @@ export class FilesPanel extends React.Component<Props, State, {}> {
           <div className="column">
             <div className="card">
               <span className="title-m black-font">{pathTitle}</span>
-              <div className="qrcode">
+              <div className="qrcode-flat">
                 <QRCode value={absDownloadURL} size={128} />
               </div>
             </div>