feat(view): solplate taper across the 교각축 직각 (thick T1 at the (−) side); 교량받침 본체 as a box

The solplate's L (A + margin) runs across the 교각축 직각 and its W (B + margin) along the 교축; the top tapers across L with
T1 at the (−) side (T1 = T + L·|S|/200). The 교량받침 본체 is one box per bearing: the solplate plan less 100 mm on each
side, from the mortar top (EL.X) up h3 = 181 mm, turned with the bearing row. It is shown with the bearing group.

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>

src/main.ts

@@ -45,7 +45,7 @@ interface Pier extends PierValues {
 type Stage = 'shape' | 'plan' | 'rebar' | 'quantity';
 
 const PART_GROUPS: { label: string; parts: PartName[] }[] = [
-  { label: '받침·받침블럭', parts: ['blocks', 'pads'] },
+  { label: '받침·받침블럭', parts: ['blocks', 'pads', 'bearings'] },
   { label: '솔플레이트', parts: ['solplates'] },
   { label: '코핑', parts: ['coping'] },
   { label: '기둥', parts: ['columns'] },