feat(view): attribute-copy dialog (시안 ⑥, plan C8)

- 속성 복사… opens the four-step dialog: source (current inputs), items,
  targets (same-type filter on by default), and a preview with changed values
  and skipped items per target. Apply changes only the visible, ticked targets.
- Items that the model does not have yet (기둥, 받침, 배근, 기초 형상) are shown
  as 예정 and disabled. Coping length and pile length are off by default.
- Option: regenerate the targets right after applying (default on); otherwise
  they show as 재생성 필요 through the normal change tracking.
- Not verified in a browser.

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

src/style.css

@@ -644,4 +644,11 @@ body { background: #eef1f4; font-family: 'Noto Sans KR', system-ui, sans-serif;
 .views .btn[aria-pressed='true'] { background: #1f5fa8; color: #ffffff; font-weight: 700; }
 .viewer-head { gap: 8px; }
 .edit-card h3 { font-size: 12px; color: #55606e; }
+/* 속성 복사 (시안 ⑥) */
+.cp-items li { display: flex; flex-wrap: wrap; align-items: center; gap: 6px 14px; padding: 6px 0; border-bottom: 1px solid #e6eaef; }
+.cp-group { min-width: 110px; font-size: 12px; font-weight: 700; color: #55606e; }
+.cp-targets { list-style: none; padding: 0; margin: 6px 0; max-height: 240px; overflow-y: auto; }
+.cp-targets li { display: flex; align-items: center; gap: 8px; min-height: 36px; }
+.chk.disabled { opacity: 0.5; }
+#cp-preview td, #cp-preview th { font-size: 12px; }