feat(svg-editor): Implement SVG shape loading and editing functionality

- Add SVG shape loading from disk, allowing users to customize shapes by placing SVG files in the designated directory.
- Introduce a new `ShapeCatalog` to manage SVG shapes, prioritizing user-defined shapes over built-in templates.
- Implement an SVG editor with node-based editing capabilities, enabling users to manipulate SVG paths directly.
- Create a new `SvgEditable` structure to represent editable SVG shapes, supporting operations like adding, removing, and moving nodes.
- Enhance the GUI with an SVG editor panel for visual editing of SVG shapes, including controls for node manipulation and saving changes.
- Ensure compatibility with existing shape tools and maintain a seamless user experience across the application.

hcie-iced-app/crates/hcie-iced-gui/src/app.rs

@@ -5010,6 +5010,14 @@ impl HcieIcedApp {
                             .engine
                             .set_active_layer(safe_source);
                     }
+                    // Snapshot shape catalog entries for CustomShape tool
+                    let custom_shapes: Vec<(String, String)> = self.documents
+                        .get(self.active_doc)
+                        .map(|d| {
+                            d.engine.shape_catalog.all().iter().map(|e| (e.kind.clone(), e.svg.clone())).collect()
+                        })
+                        .unwrap_or_default();
+
                     let engine = &mut self.documents[self.active_doc].engine;
                     let color = self.fg_color;
                     let stroke = self.settings.tool_settings.vector_stroke_width;
@@ -5222,6 +5230,20 @@ impl HcieIcedApp {
                                 _ => unreachable!(),
                             }
                         }
+                        Tool::CustomShape(idx) => {
+                            let entry = custom_shapes.get(idx as usize);
+                            match entry {
+                                Some((kind, svg)) => Some(hcie_engine_api::VectorShape::SvgShape {
+                                    x1: x0.min(x1), y1: y0.min(y1),
+                                    x2: x0.max(x1), y2: y0.max(y1),
+                                    kind: kind.clone(),
+                                    svg: svg.clone(),
+                                    stroke, color, fill_color: color, fill: true,
+                                    angle: 0.0, opacity, hardness: 0.5,
+                                }),
+                                None => None,
+                            }
+                        }
                         _ => None,
                     };