feat(ui): use the shared colour selector in properties, ribbon and layers

Replace the bespoke colour pickers with the shared color_selector / color_list
widget so colour selection is identical everywhere:
- left properties panel (selected entities' colour)
- ribbon Home-tab colour dropdown
- layer manager per-layer colour

Each routes its "More…" entry to the standalone Select Color window via a
ColorPickTarget (Properties / Ribbon / Layer). Extracted color_list as the
shared popup content; the colour selector button now fills its container.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/mod.rs

@@ -574,6 +574,12 @@ pub enum ColorPickTarget {
     DimStyle(DsField),
     MLeader(&'static str),
     Table(u8, &'static str),
+    /// Selected entities' colour (left properties panel).
+    Properties,
+    /// Current creation colour (ribbon).
+    Ribbon,
+    /// A layer's colour, by panel row index.
+    Layer(usize),
 }
 
 /// Identifies a DimStyle field that can be edited in the dialog.

src/app/update.rs

@@ -7330,6 +7330,10 @@ impl OpenCADStudio {
                 self.ds_color_open = None;
                 self.mls_color_open = None;
                 self.ts_color_open = None;
+                self.ribbon.close_dropdown();
+                let i = self.active_tab;
+                self.tabs[i].properties.color_picker_open = false;
+                self.tabs[i].layers.color_picker_row = None;
                 if let Some(id) = self.color_pick_window {
                     return window::gain_focus(id);
                 }
@@ -7356,6 +7360,19 @@ impl OpenCADStudio {
                             value: s,
                         })
                     }
+                    Some(crate::app::ColorPickTarget::Properties) => {
+                        Some(Message::PropColorChanged(color))
+                    }
+                    Some(crate::app::ColorPickTarget::Ribbon) => {
+                        Some(Message::RibbonColorChanged(color))
+                    }
+                    Some(crate::app::ColorPickTarget::Layer(idx)) => {
+                        self.tabs[self.active_tab].layers.selected = Some(idx);
+                        match color {
+                            acadrust::types::Color::Index(i) => Some(Message::LayerColorSet(i)),
+                            _ => None,
+                        }
+                    }
                     None => None,
                 };
                 let mut tasks = Vec::new();