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/l10n/app_localizations.dart

@@ -137,7 +137,7 @@ abstract class AppLocalizations {
   /// No description provided for @shortcutsList.
   ///
   /// In en, this message translates to:
-  /// **'• Left/Right arrow — previous/next image\n• Ctrl+S — save visible area (JPEG 93)\n• Ctrl+Q — close window\n• Ctrl+Shift+Q — close all windows\n• Double click — toggle fill/fit\n• Right-drag — contrast\n• Shift+right-drag — rotate\n• Ctrl+right-drag — saturation\n• Ctrl+Shift+right-drag — brightness\n• R — flip horizontally (resets effects, press again to undo)'**
+  /// **'• Left/Right arrow — previous/next image\n• Ctrl+S — save visible area (JPEG 93)\n• Ctrl+R — flip horizontally (clears effects, press again to undo)\n• Ctrl+Q — close window\n• Ctrl+Shift+Q — close all windows\n• Double click — toggle fill/fit\n• Right-drag — contrast\n• Shift+right-drag — rotate\n• Ctrl+right-drag — saturation\n• Ctrl+Shift+right-drag — brightness'**
   String get shortcutsList;
 
   /// No description provided for @print.