Neko cat v1.4.0 (#4635)

**feat:** Added Neko Dog, context menus, and multi‑monitor improvements.

### Added
- **Neko Dog:** New desktop companion, selectable in settings or mixed with existing litters.  
- **Right‑Click Menu:** Quickly change behaviors (Chase Mouse, Pace, Play With Window).  
- **Save Last Behavior:** Companions now remember their active behavior after restart.  

### Improved
- **Multi‑Monitor Bounds:** Behaviors now align correctly to the monitor edges.  
- **Run Around Physics:** Natural rest cycles (~45s play, ~15s nap) and realistic ball physics with angles/reflections.  
- **Leg Animations:** Walking/running animations scale to actual distance traveled (improved overall animation).
- **Drag & Drop:** Dropping a companion resumes their previous behavior (except Play With Window mode).  
- **Behavior Logic:** Smoother movement and state transitions.  
- **Assets:** Downloads now point to latest commit including Neko Dog assets.  

### Fixed
- **Multi‑Monitor Bugs:** Companions no longer go off‑screen or get stuck.  
- **Window Maximizing:** Double‑clicking companions no longer maximizes underlying windows.  
- **Theme Switcher Leak:** Cleaned up dynamic theme loading to prevent memory leaks.

Author: ciizerr