feat(plot): plot device model with AutoCAD names and printable areas

A page setup names its plotter, and AutoCAD looks that name up in its own
configurations: `DWG To PDF.pc3` for PDF output, the spooler name for a
system printer, `None` when nothing is assigned. Drawings saved here used
to carry the dialog's label ("Save to PDF file…"), so AutoCAD reported a
missing device on every layout plotted to PDF from Open CAD Studio.

- New `io::plot_device`: `PlotDevice { None, Pdf, Printer }` with AutoCAD's
  spellings, a reader for stored names that keeps any plotter
  configuration AutoCAD wrote (an HP `.pc3`, `DWF6 ePlot.pc3` — plotted to
  PDF here but preserved for AutoCAD) and upgrades the legacy label.
- Printable areas: the PDF driver's margins per sheet variant (full bleed
  edge to edge; standard / expand insets provisional until read off
  AutoCAD's plotter configuration), and for CUPS printers the media and
  margins the queue reports over IPP (`ipptool` `media-col-database`),
  parsed once per printer and cached. Windows enumeration follows with
  native GDI printing.
- Page setups now store the device in AutoCAD's spelling and the margins
  of the chosen device/sheet, keeping the drawing's own values while
  neither changed (AutoCAD's `PAPERUPDATE` behaviour). The paper-space
  printable-area rectangle follows.
- Plot dialog: the default entry names the printer it resolves to; a
  printer that answered lists its own sheets with a note; the media query
  runs in the background and answers for a since-deselected printer are
  dropped.

Tests: device names, stored-name resolution, PDF margin table, IPP media
parsing (sizes, margins, borderless folding, default sheet), PWG names,
plus dialog ↔ layout round-trips for PDF, legacy label, preserved plotter
configuration, sheet change → margins, and printer selection.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

locales/ru-RU/opencadstudio.ftl

@@ -5014,6 +5014,7 @@ plot =
     .export-pdf = Экспорт PDF
     .fit-to-paper = Вписать в лист
     .layout-plots-the-current-sheet-using-the-selec = Лист печатается на выбранном формате бумаги.
+    .sheet-sizes-and-printable-areas-reported-by-th = Sheet sizes and printable areas reported by the printer.
     .merge-overlapping-lines = Слияние пересекающихся линий
     .object-lineweights = Весы для объектов
     .orientation = Ориентация