DKR-R v1.0.7 beta 6 - ModernCamera++ shadow fix

Camera++ now keeps the vehicle shadow tied to its own racer and viewport.
Its private redraw uses DKR-R's existing canonical shadow interpolation,
including the vehicle-specific shadow handling, instead of leaving projected
shadow vertices at the authored frame while the vehicle moves between frames.

Camera cuts, track changes and vehicle changes keep separate shadow history.
The shadow fix does not change race logic, saves or online synchronisation.
The recent launcher cleanup and optional ModernCamera++ mod are included.

This is a flat-screen playtest. VR output is not enabled yet.
Compiled and packaged only. Gameplay and visual testing remain with the user.
