- Allow users to select a transparent color for logo images (watermarks) via UI (checkbox, color picker, preview).
- Apply color-key transparency in both System.Drawing and ImageSharp backends: specified color in logo is made fully transparent.
- Persist transparency settings in PicSettings and SettingsDto; bind to DataModel and UI controls.
- Update logo preview to reflect transparency in real time.
- Add option to select image processing library (System.Drawing or ImageSharp) in UI and settings.
- Fix bug in SettingsService parameter loading for int/double/DateTime.
- Fully integrate color-key transparency into image processing and settings serialization.
Dialogs now remember last-used folders for source, destination, logo, and settings files by storing these paths in a user preferences file under LocalApplicationData. Preferences are saved on form close, reducing unnecessary writes. SettingsService now uses a temporary ParametriSetup for settings files to avoid polluting user preferences. Error handling ensures preference save failures do not disrupt the user. This separation improves user experience and keeps user preferences distinct from project settings.
