fix: Holdings dropdown searcher locked

Set the `KeyNavigation.backtab` to itself to avoid accidentally pressing
`Shift+Tab` and tab away from the focused `StatusInput` (which makes it
look like it's disabled)

Fixes #10561

ui/app/AppLayouts/Chat/controls/community/EnsPanel.qml

@@ -66,6 +66,8 @@ ColumnLayout {
                 addOrUpdateButton.clicked()
         }
 
+        KeyNavigation.backtab: domainNameInput
+
         Component.onCompleted: {
             if (text) {
                 input.dirty = true

ui/app/AppLayouts/Chat/controls/community/ExtendedDropdownContent.qml

@@ -393,6 +393,8 @@ Item {
                 return qsTr("Search collectibles")
             }
 
+            KeyNavigation.backtab: searcher
+
             Binding on placeholderText {
                 when: d.currentItemName !== ""
                 value: qsTr("Search %1").arg(d.currentItemName)