Phase 7: Plot settings and PDF export

- Add printpdf 0.9.1 dependency for native PDF generation.
- New src/io/pdf_export.rs: converts paper-space WireModels to a PDF
  page (per-wire stroke color, line weight in Pt, NaN-split segments).
  White/near-white colors are inverted to black for print output.
- Add PlotExport / PlotExportPath messages: opens a save-file dialog
  and writes a .pdf next to the drawing file.
- Add PageSetupOpen/Close/WidthEdit/HeightEdit/Commit messages: a
  centered modal panel lets the user enter paper width and height (mm);
  on commit the Layout object's min/max_limits are updated in-place.
- Register PRINT / PLOT / EXPORT and PAGESETUP (PS) commands in
  dispatch_command; fix MVIEW error message to English.
- Layout ribbon gains a "Plot" group with Page Setup and Export PDF
  ribbon buttons.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/commands.rs

@@ -892,7 +892,7 @@ impl H7CAD {
             // ── Layout / viewport ──────────────────────────────────────────
             "MVIEW"|"MV" => {
                 if self.tabs[i].scene.current_layout == "Model" {
-                    self.command_line.push_error("MVIEW: önce bir paper space layout'una geçin.");
+                    self.command_line.push_error("MVIEW: switch to a paper space layout first.");
                 } else {
                     use crate::modules::layout::mview::MviewCommand;
                     let new_cmd = MviewCommand::new();
@@ -901,6 +901,18 @@ impl H7CAD {
                 }
             }
 
+            // ── Plot / Page Setup ──────────────────────────────────────────
+            "PRINT"|"PLOT"|"EXPORT" => {
+                return Task::done(Message::PlotExport);
+            }
+            "PAGESETUP"|"PS" => {
+                if self.tabs[i].scene.current_layout == "Model" {
+                    self.command_line.push_error("PAGESETUP: switch to a paper space layout first.");
+                } else {
+                    return Task::done(Message::PageSetupOpen);
+                }
+            }
+
             _ => self.command_line.push_error(&format!("Unknown command: {cmd}")),
         }