feat(scene): draw nonprint light, camera and geo-location glyphs

Lights, camera views and the geographic-location marker had no on-screen
representation. Add display glyphs for all three:

- Lights render through a new EntityType::Light: a cone/flashlight for spot
  lights, a wire sphere for point lights, a sun for distant lights, sized in
  screen space (fixed-world fallback).
- Camera views (perspective VIEW records) and the GEODATA "daisy" marker are
  synthesized into the model-space resident wire set from the document, since
  they are not entities.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/entities/mod.rs

@@ -9,6 +9,7 @@ pub mod hatch;
 pub mod helix;
 pub mod insert;
 pub mod leader;
+pub mod light;
 pub mod line;
 pub mod lwpolyline;
 pub mod mesh;