feat: embed images (OLE2FRAME), print pipeline fixes, plot prefs, community fonts

- IMAGEEMBED: pack raster images into OLE2FRAME entities so a .dwg is
  self-contained; 'Embed Image' entry in the XREF attach menu; control/MCP
  op embed_image for external tools; dxf_name for OLE2FRAME queries.
- Scene: populate_images_from_document now rebuilds OLE2FRAME and PDF
  underlay models too (they used to vanish after any XREF op).
- Printing: add PRINTER_ENUM_NETWORK pass when listing printers; GDI
  spooler fallback (hayro raster at 300 DPI + StretchDIBits) for hosts
  whose PDF handler registers no print verb; DEVMODE orientation with a
  90-degree raster rotation fallback for v4 drivers; fix the fit-scale
  precedence bug that printed blank pages.
- PDF export dialogs on Windows use the async file dialog so the native
  overwrite confirmation no longer deadlocks the UI thread.
- Plot dialog: persist the chosen printer (saved on selection) and the
  picked plot window across sessions; page setups with no device no
  longer reset the output device.
- Community fonts: detect unresolvable .shx references on open and offer
  a download from the repository's fonts/ folder (contribution guide in
  fonts/README.md); custom font source URL setting for intranet font
  servers; downloaded fonts resolve from the per-user fonts directory.

src/app/control/actions.rs

@@ -67,7 +67,54 @@ pub(super) const NAMES: &[&str] = &[
     "undo",
     "redo",
 ];
+
+/// Parse the `at` placement point for `embed_image`: `[x,y]` or `[x,y,z]`.
+fn embed_point(req: &Value) -> Result<acadrust::types::Vector3, Value> {
+    let values = req["at"]
+        .as_array()
+        .filter(|v| (2..=3).contains(&v.len()))
+        .ok_or_else(|| failure("invalid_point", "Expected at:[x,y] or [x,y,z]"))?;
+    let mut p = [0.0_f64; 3];
+    for (i, v) in values.iter().enumerate() {
+        p[i] = v
+            .as_f64()
+            .filter(|v| v.is_finite())
+            .ok_or_else(|| failure("invalid_point", "Expected finite coordinates"))?;
+    }
+    Ok(acadrust::types::Vector3::new(p[0], p[1], p[2]))
+}
 impl OpenCADStudio {
+    /// `embed_image` — pack the picture at `path` into an OLE2FRAME placed
+    /// with its lower-left corner at `at` (default width ≈ pixel_width/100,
+    /// like the interactive command's Enter answer) and commit it as one
+    /// undo step. The drawing stays self-contained: no external file to lose.
+    #[cfg(not(target_arch = "wasm32"))]
+    pub(super) fn control_embed_image(&mut self, req: &Value) -> Result<Task<Message>, Value> {
+        let i = self.active_tab;
+        let path = string(req, "path")?;
+        let image = crate::io::ole_embed::EmbeddedImage::from_file(std::path::Path::new(&path))
+            .map_err(|e| failure("embed_failed", e))?;
+        let at = embed_point(req)?;
+        let default_width = (image.pixel_width as f64 / 100.0).max(1.0);
+        let width = req["width"].as_f64().filter(|w| *w > 0.0).unwrap_or(default_width);
+        self.push_undo_snapshot(i, "IMAGEEMBED");
+        let handle = crate::io::ole_embed::add_embedded_image(
+            &mut self.tabs[i].scene.document,
+            &image,
+            at,
+            width,
+        )
+        .map_err(|e| failure("embed_failed", e))?;
+        self.post_ref_op(i);
+        self.set_control_result(json!({
+            "handle": format!("{:X}", handle.value()),
+            "kind": "Ole2Frame",
+            "path": path,
+            "width": width,
+        }));
+        Ok(Task::none())
+    }
+
     pub(super) fn control_properties(&mut self) -> Value {
         self.refresh_properties();
         json!({"ok":true,"sections":self.tabs[self.active_tab].properties.sections.iter().map(|s|json!({"title":s.title,"properties":s.props.iter().map(|p|{