feat(render): draw DGN line-style symbols on linetypes

Linetypes converted from MicroStation DGN keep their pattern in DGN line-style
objects (empty standard LTYPE), so entities using them drew as a plain line and
lost the symbols (e.g. a pipe's end circles). Walk the line-style tree
(resolved by name to its LSDefinition), collect the symbol components' anonymous
blocks, and draw each at the host polyline's endpoints, scaled by the symbol's
decoded scale (geometry / scale) so it matches the drawing (verified: a 0.75
ellipse renders at the file's intended 0.375 radius).

Bumps acadrust to 8e18c6b (DGN line-style symbol-scale decode). First pass: the
stroke dash pattern and exact per-vertex placement need more of the line-style
leaf decoded; the base line still draws solid.

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

src/scene/convert/mod.rs

@@ -18,6 +18,7 @@ pub mod acis_to_truck {
         None
     }
 }
+pub mod dgn_linestyle;
 pub mod truck_tess;
 pub mod tessellate;
 pub(crate) mod tess;