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/ru-RU/opencadstudio.ftl

@@ -686,6 +686,7 @@ common =
     .layers = Слои
     .layout = Расположение
     .layout-name-silindi = Лист «__ocs_fmt_0__» удалён
+    .layout-copied = Layout "__ocs_fmt_0__" copied as "__ocs_fmt_1__"
     .layout-new-name-created-use-mview-to-add-a-vie = Создан лист «__ocs_fmt_0__» — используйте MVIEW для добавления видового экрана
     .layout-orig-new-name = Выравнивание "__ocs_fmt_0__" → "__ocs_fmt_1__"
     .layout-name-created = Создан лист «__ocs_fmt_0__».