chore: cleanup unused code in QrScanner and remove vue-qrcode-reader dependency

src/components/tools/QrScanner.vue

@@ -228,20 +228,10 @@ const onDetect = (detectedCodes) => {
   processCodes(validCodes)
 }
 
-const onCameraOn = async () => {} // Removed
-
-const ensureFrontMirror = () => {} // Removed
-
-const startFrontMirrorObserver = () => {} // Removed
-
-const stopFrontMirrorObserver = () => {} // Removed
-
 watch(facingMode, () => {
   startScan()
 })
 
-const paintDetections = () => {} // Removed, we don't paint detections on video anymore (too complex without overlay canvas)
-
 const onError = (err) => {
   if (err.name === 'NotAllowedError') {
     error.value = 'Camera permission denied'