add class names for UI testing

frontend/src/App.tsx

@@ -457,7 +457,7 @@ function App() {
                     </div>
                     <Button
                       onClick={doUpdate}
-                      className="dark:text-white dark:bg-gray-700"
+                      className="dark:text-white dark:bg-gray-700 update-btn"
                     >
                       Update
                     </Button>
@@ -574,7 +574,7 @@ function App() {
                       <Button
                         onClick={downloadCode}
                         variant="secondary"
-                        className="flex items-center gap-x-2 mr-4 dark:text-white dark:bg-gray-700"
+                        className="flex items-center gap-x-2 mr-4 dark:text-white dark:bg-gray-700 download-btn"
                       >
                         <FaDownload /> Download
                       </Button>

frontend/src/components/ImageUpload.tsx

@@ -166,7 +166,7 @@ function ImageUpload({ setReferenceImages }: Props) {
       {screenRecorderState === ScreenRecorderState.INITIAL && (
         /* eslint-disable-next-line @typescript-eslint/no-explicit-any */
         <div {...getRootProps({ style: style as any })}>
-          <input {...getInputProps()} />
+          <input {...getInputProps()} className="file-input" />
           <p className="text-slate-700 text-lg">
             Drag & drop a screenshot here, <br />
             or click to upload

frontend/src/components/UrlInputSection.tsx

@@ -69,7 +69,7 @@ export function UrlInputSection({ doCreate, screenshotOneApiKey }: Props) {
       <Button
         onClick={takeScreenshot}
         disabled={isLoading}
-        className="bg-slate-400"
+        className="bg-slate-400 capture-btn"
       >
         {isLoading ? "Capturing..." : "Capture"}
       </Button>