feat: crop save (save visible area at original resolution) v1.4.0

- Save visible area at original resolution as JPEG q90 (title bar button or Ctrl+S)
- Output name: original name + _HHmmss suffix; no overwrite, warning shown
- Active color effects baked in; rotation saves bounding box
- New: crop_save_service, l10n strings TR/EN, docs/plan-crop-save.md

lib/widgets/custom_title_bar.dart

@@ -3,9 +3,10 @@ import 'package:window_manager/window_manager.dart';
 
 class CustomTitleBar extends StatelessWidget {
   final VoidCallback? onSettings;
+  final VoidCallback? onSaveCrop;
   final bool visible;
 
-  const CustomTitleBar({super.key, this.onSettings, this.visible = true});
+  const CustomTitleBar({super.key, this.onSettings, this.onSaveCrop, this.visible = true});
 
   @override
   Widget build(BuildContext context) {
@@ -43,6 +44,11 @@ class CustomTitleBar extends StatelessWidget {
                 child: Row(
                   mainAxisSize: MainAxisSize.min,
                   children: [
+                    if (onSaveCrop != null)
+                      _BarButton(
+                        icon: Icons.save_outlined,
+                        onTap: onSaveCrop!,
+                      ),
                     _BarButton(
                       icon: Icons.horizontal_rule,
                       onTap: () => windowManager.minimize(),