fix: Ctrl+R flip also matches the physical R key (v1.6.1)

On some keymaps the R key resolves to a different logical key (observed on a
Turkish remote-desktop setup: the R key arrives as logical T), so the Ctrl+R
shortcut never fired even though the key events reached the app. The shortcut
now matches PhysicalKeyboardKey.keyR as well; a regression test covers the
wrong-layout case.

lib/widgets/image_canvas.dart

@@ -166,13 +166,6 @@ class ImageCanvasState extends State<ImageCanvas> {
   bool _onHardwareKey(KeyEvent event) {
     final key = event.logicalKey;
     if (event is KeyDownEvent) {
-      if (key == LogicalKeyboardKey.keyR &&
-          !HardwareKeyboard.instance.isControlPressed &&
-          !HardwareKeyboard.instance.isShiftPressed &&
-          !HardwareKeyboard.instance.isAltPressed) {
-        _toggleFlipH();
-        return true;
-      }
       if (key == LogicalKeyboardKey.controlLeft ||
           key == LogicalKeyboardKey.controlRight) {
         _ctrlPressed = true;
@@ -224,8 +217,8 @@ class ImageCanvasState extends State<ImageCanvas> {
     _markRenderDirty();
   }
 
-  /// R: sağ çift tık gibi efektleri sıfırlar ve yatay aynalar; tekrar basınca geri alır.
-  void _toggleFlipH() {
+  /// Ctrl+R: sağ çift tık gibi efektleri sıfırlar ve yatay aynalar; tekrar basınca geri alır.
+  void toggleFlipH() {
     _flipH = !_flipH;
     _angle = 0; _contrast = 1.0; _saturation = 1.0; _brightness = 0;
     _interactionMode = 'none';