IMAGEADJUST: Image Adjust dialog for raster images

IMAGEADJUST (alias IAD) takes the selected raster images or asks
"Select image(s):", then opens a dialog with a before/after preview of
the first image and brightness, contrast and fade rows (bar plus
stepper, whole numbers 0-100). Apply writes the values to every chosen
image as one undo step; restore defaults sets 50/50/0. Adds the
image_adjust automation action and the image-adjust locale group.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/app/mod.rs

@@ -582,6 +582,8 @@ pub(super) struct OpenCADStudio {
     pc_section: Option<crate::ui::window::pdf_dialogs::PcSectionState>,
     /// -VIEW sEttings Background dialog.
     view_background: Option<crate::ui::window::pdf_dialogs::ViewBackgroundState>,
+    /// IMAGEADJUST dialog.
+    image_adjust: Option<crate::ui::window::pdf_dialogs::ImageAdjustState>,
     underlay_layers: Option<crate::ui::window::pdf_dialogs::UnderlayLayersState>,
     pdf_import_settings: Option<crate::modules::insert::pdf_import::PdfImportSettings>,
     pdf_import_file: Option<crate::ui::window::pdf_dialogs::PdfImportFileState>,
@@ -2153,6 +2155,7 @@ pub enum ModalKind {
     PointCloudColorMap,
     PcSection,
     ViewBackground,
+    ImageAdjust,
     UnderlayLayers,
     PdfImportSettings,
     PdfImportFile,
@@ -4559,6 +4562,7 @@ impl OpenCADStudio {
             point_cloud_color_map: None,
             pc_section: None,
             view_background: None,
+            image_adjust: None,
             underlay_layers: None,
             pdf_import_settings: None,
             pdf_import_file: None,