ifcviewer: move camera + surface-geom state into ViewportCore (#84-g)

Move the camera/projection/clear-color fields that buildViewProj,
updateFrameUniforms, the cull screen-area projector, and the bonsai-
side cameraState/setCamera/viewAll surface depend on. Same alias
pattern; no method bodies move in this commit — the next one moves
the camera math methods now that all their state is in core.

State moved (12 fields):
  int   configured_w_, configured_h_
  float camera_target_[3], camera_distance_
  float camera_yaw_deg_, camera_pitch_deg_, camera_fov_y_deg_
  float camera_near_, camera_far_
  bool  projection_ortho_
  Eigen::Vector4f background_color_

ViewportWindow keeps reference aliases for each (including a proper
`float (&camera_target_)[3]` reference-to-array binding) so the
~150 call sites that touch camera state stay unchanged. Aliases
collapse when their owning methods migrate.

Builds: desktop / bonsai / web all green. Tests 100/100.

src/ifcviewer/ViewportWindow.cpp

@@ -608,7 +608,18 @@ ViewportWindow::ViewportWindow(QWindow* parent)
       next_model_id_  (core_.next_model_id_),
       next_object_id_ (core_.next_object_id_),
       federated_false_origin_meters_(core_.federated_false_origin_meters_),
-      wgpu_initialized_(core_.wgpu_initialized_) {
+      wgpu_initialized_(core_.wgpu_initialized_),
+      configured_w_   (core_.configured_w_),
+      configured_h_   (core_.configured_h_),
+      camera_target_  (core_.camera_target_),
+      camera_distance_(core_.camera_distance_),
+      projection_ortho_(core_.projection_ortho_),
+      camera_yaw_deg_ (core_.camera_yaw_deg_),
+      camera_pitch_deg_(core_.camera_pitch_deg_),
+      camera_fov_y_deg_(core_.camera_fov_y_deg_),
+      camera_near_    (core_.camera_near_),
+      camera_far_     (core_.camera_far_),
+      background_color_(core_.background_color_) {
     // wgpu doesn't need a GL context; we just need a real native window
     // whose backing layer matches the GPU API wgpu will drive.
     //