feat: add shape fill/stroke transparency, RGBA color picker, and dash styles

Closes #193. Shapes now support no-fill and no-stroke toggles for drawing
outlines or fill-only shapes. Adds RGBA color picker with opacity control,
stroke dash styles (solid/dashed/dotted), and i18n for all shape labels.

packages/shared/src/i18n/it.ts

@@ -1373,6 +1373,27 @@ export const it: TranslationKeys = {
     errors: {
       serverDecodeFailed: "Decodifica del server non riuscita",
     },
+    shapes: {
+      shape: "Shape",
+      fill: "Fill",
+      stroke: "Stroke",
+      strokeWidth: "Width",
+      cornerRadius: "Radius",
+      sides: "Sides",
+      points: "Points",
+      dashStyle: "Dash",
+      solid: "Solid",
+      dashed: "Dashed",
+      dotted: "Dotted",
+      none: "None",
+      opacity: "Opacity",
+      rectangle: "Rectangle",
+      ellipse: "Ellipse",
+      line: "Line",
+      arrow: "Arrow",
+      polygon: "Polygon",
+      star: "Star",
+    },
   },
   settings: {
     heading: "Impostazioni",