qml: refactor qr scan to qt6

As the method of capturing frames is totally different, the animation when
a QR is found has been removed.

electrum/gui/qml/components/SendDialog.qml

@@ -19,6 +19,11 @@ ElDialog {
     padding: 0
     topPadding: 0
 
+    onAboutToHide: {
+        console.log('about to hide')
+        qrscan.stop()
+    }
+
     function restart() {
         qrscan.restart()
     }
@@ -34,6 +39,13 @@ ElDialog {
         }
     }
 
+    // override
+    function doClose() {
+        console.log('SendDialog doClose override') // doesn't trigger when going back??
+        qrscan.stop()
+        Qt.callLater(doReject)
+    }
+
     ColumnLayout {
         anchors.fill: parent
         spacing: 0
@@ -55,7 +67,10 @@ ElDialog {
                 Layout.preferredWidth: 1
                 icon.source: '../../icons/copy_bw.png'
                 text: qsTr('Paste')
-                onClicked: dialog.dispatch(AppController.clipboardToText())
+                onClicked: {
+                    qrscan.stop()
+                    dialog.dispatch(AppController.clipboardToText())
+                }
             }
         }