refactor: remove the legacy full view_proj (CPU cull now relative-to-eye)

The GPU draws exclusively via the rotation-only `view_rot` + eye double-
single; the full view-projection survived only to project AABBs in the
CPU frustum-cull / scissor / LOD passes. Migrate those to the same
relative-to-eye math (project `point - eye` through `view_rot`) — pixel-
equivalent but precise at UTM scale — then drop the dead uniform:

- pipeline cull/scissor/LOD helpers take (view_rot, eye) instead of the
  full view_proj; render.rs reconstructs eye from the uniform's
  eye_high/eye_low and passes the cropped view_rot.
- Remove the `view_proj` field from the shared Uniforms struct and all six
  shader structs that only declared it for layout (none read it), and
  delete Camera::view_proj(). The struct shrinks by one mat4 on both
  sides, keeping the Rust / WGSL layouts in lock-step.

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

src/scene/pipeline/uniforms.rs

@@ -4,11 +4,6 @@ use iced::Rectangle;
 #[derive(Copy, Clone, Debug, bytemuck::Pod, bytemuck::Zeroable)]
 #[repr(C)]
 pub struct Uniforms {
-    /// Full view-projection (with translation) — GPU rendering no longer uses
-    /// this; it remains for the CPU-side frustum-cull / scissor / LOD passes
-    /// that project offset-relative AABBs to screen. The GPU draws via the
-    /// relative-to-eye `view_rot` + `eye_high`/`eye_low` below.
-    pub view_proj: glam::Mat4,
     pub viewport_size: [f32; 2],
     /// World units per screen pixel at the current zoom. Used by the
     /// hatch shader to substitute solid fill when pattern line spacing
@@ -54,7 +49,6 @@ impl Uniforms {
         };
         let (eye_high, eye_low) = camera.eye_high_low();
         Self {
-            view_proj: camera.view_proj(bounds),
             viewport_size: [bounds.width, bounds.height],
             world_per_pixel,
             lwdisplay_enable: if lwdisplay_enable { 1.0 } else { 0.0 },