PaintFE v1.2.6

Highlights
- New non-destructive layer masks are now fully integrated into the layer workflow.
- Editing reliability improved across tools with safer auto-commit behavior on layer switches.
- UI and theming got a broad polish pass, especially for light themes and control customization.

What's new
- Layer Masks
- Add layer mask (reveal all)
- Add layer mask from selection
- Toggle mask editing and paint directly on masks
- Enable or disable masks
- Invert, apply, or delete masks
- Undo and redo support for mask painting and mask operations

- Tools and Editing
- Tool previews now commit automatically when changing layers
- Shapes edits now record correctly in history
- Shapes now include side stretch handles
- Align tool can target selection bounds
- Triangle shape alignment and centering improved

- Text and Fonts
- Fedora and Linux text input path improvements
- Font dropdown behavior restored to pre-egui-update expectations
- Hovering text-layer settings gear now shows a pointing cursor

- UI and Theme
- Better icon contrast and behavior on lighter themes
- New interface customization controls for tool shelf, icon buttons, steppers, and text input backgrounds
- Effects and Atmosphere interface settings section removed for a cleaner settings surface

- Fixes and Maintenance
- Degree symbol rendering fixed in relevant effect dialogs
- Hover-and-delete in Layers panel now deletes the hovered active layer as expected
- Non-fatal X11/xkb Compose parse noise reduced in AppImage launcher setup
- Updated triangle shape goldens and lint-cleaned release branch