feat(renderer): add Blinn-Phong shader, light uniforms, mesh pipeline

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

crates/voltex_renderer/src/lib.rs

@@ -1,4 +1,5 @@
 pub mod gpu;
+pub mod light;
 pub mod obj;
 pub mod pipeline;
 pub mod vertex;
@@ -6,5 +7,6 @@ pub mod mesh;
 pub mod camera;
 
 pub use gpu::{GpuContext, DEPTH_FORMAT};
+pub use light::{CameraUniform, LightUniform};
 pub use mesh::Mesh;
 pub use camera::{Camera, FpsController};