- 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.
Enhanced speed counter with smoothing and elapsed time display.
Added folder open buttons to UI and repositioned speed label.
Added UpdateSubdirectories to settings for persistence.
