feat(layout): copy a layout from its tab menu (#1822)

The layout tab's right-click menu gains New Layout, Copy, Page Setup
and Plot beside Rename and Delete. Copy makes "<name> (2)" with the
source's page setup, sheet view and every paper-space object,
viewports included, and opens it.

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

locales/ko-KR/opencadstudio.ftl

@@ -682,6 +682,7 @@ common =
     .layers = 레이어
     .layout = 레이아웃
     .layout-name-silindi = 레이아웃 "__ocs_fmt_0__" 삭제됨
+    .layout-copied = Layout "__ocs_fmt_0__" copied as "__ocs_fmt_1__"
     .layout-new-name-created-use-mview-to-add-a-vie = "__ocs_fmt_0__" 레이아웃이 생성되었습니다. MVIEW를 사용하여 뷰포트를 추가하세요.
     .layout-orig-new-name = 레이아웃 "__ocs_fmt_0__" → "__ocs_fmt_1__"
     .layout-name-created = '__ocs_fmt_0__' 레이아웃이 생성되었습니다.