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 <[email protected]>

src/modules/layout/mod.rs

@@ -3,7 +3,7 @@
 
 pub mod mview;
 
-use crate::modules::{CadModule, RibbonGroup};
+use crate::modules::{CadModule, IconKind, ModuleEvent, RibbonGroup, ToolDef};
 
 pub struct LayoutModule;
 
@@ -16,9 +16,30 @@ impl CadModule for LayoutModule {
     }
 
     fn ribbon_groups(&self) -> Vec<RibbonGroup> {
-        vec![RibbonGroup {
-            title: "Viewport",
-            tools: vec![mview::tool().into()],
-        }]
+        vec![
+            RibbonGroup {
+                title: "Viewport",
+                tools: vec![mview::tool().into()],
+            },
+            RibbonGroup {
+                title: "Plot",
+                tools: vec![
+                    ToolDef {
+                        id: "PAGESETUP",
+                        label: "Page Setup",
+                        icon: IconKind::Glyph("📋"),
+                        event: ModuleEvent::Command("PAGESETUP".to_string()),
+                    }
+                    .into(),
+                    ToolDef {
+                        id: "PLOT",
+                        label: "Export PDF",
+                        icon: IconKind::Glyph("🖨"),
+                        event: ModuleEvent::Command("PLOT".to_string()),
+                    }
+                    .into(),
+                ],
+            },
+        ]
     }
 }