- Add Serialize/Deserialize to Notification and Hints types
- Save history to ~/.local/share/garnotify/history.json on shutdown
- Load history from file on daemon startup
- Enable persistence by default (config: history.persist)

- Add animation module with state machine (Appearing, Visible, Reflowing, Disappearing, Hidden)
- Slide-in animation when notifications appear
- Slide-out animation when notifications close
- Stack reflow: remaining notifications animate up when one closes
- Configurable animation duration and slide direction

Handle mouse motion for button hover effects, and detect clicks
on action buttons to emit ActionInvoked signals.

Use gartk-x11 monitor detection to position notifications on the
correct monitor. Supports primary, mouse, and named monitor selection.

Load and render icons in notification popups. Icons are
centered vertically and positioned before the text content.

Load icons from theme directories, file paths, and D-Bus image-data hints.
Uses resvg for SVG rendering, image crate for raster formats.