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

.gitignore

@@ -49,4 +49,7 @@ app.*.map.json
 *.tar.gz
 *.exe
 deb/usr/lib/imajviewer/
-release/
+release/
+
+# Local backup snapshots (see soul.md §5)
+docs/.bak/