test: add data-testid attributes to Scanner component

frontend/components/Scanner.tsx

@@ -230,7 +230,7 @@ export default function Scanner({ onScanSuccess, onOCRMatch, paused }: ScannerPr
           </div>
         </div>
 
-        <div id={scannerId} className="w-full h-full bg-surface object-cover" />
+        <div id={scannerId} data-testid="camera-indicator" className="w-full h-full bg-surface object-cover" />
 
         {/* Selection UI */}
         {isSelecting && capturedImage && (
@@ -321,6 +321,7 @@ export default function Scanner({ onScanSuccess, onOCRMatch, paused }: ScannerPr
                     setZoom(nextZoom);
                   }
                 }}
+                data-testid="zoom-control"
                 aria-label={`Zoom ${zoom.toFixed(1)}x`}
                 className="h-14 px-5 bg-slate-800/80 hover:bg-slate-700 border border-slate-700 text-white rounded-2xl flex flex-col items-center justify-center shadow-lg cursor-pointer transition-all active:scale-95 shrink-0 focus:ring-2 focus:ring-blue-500 focus:outline-none"
               >