accessibility: implement keyboard navigation for 3D object raycaster target selection

[SourabhX16]

Problem Statement

Selecting 3D objects in AsteroidField requires a mouse pointer click on WebGL canvas.

Why It Matters

Keyboard-only users cannot select or inspect 3D space objects directly.

Expected Behaviour

Support cycling selection through nearby 3D objects using keyboard keys (e.g. [ and ]) and Enter to select.

Acceptance Criteria

• Key combinations [ and ] cycle selection through nearby orbital objects.
• Enter key triggers camera tracking and opens AsteroidCard inspector.
• Accessible keyboard selection complete.

Likely Affected Files / Components

• src/components/KeyboardManager.tsx
• src/components/AsteroidField.tsx