code-review-fix task 12.2: replace @ts-ignore with proper CSS custom property type assertion in Toolbox.tsx

src/components/Toolbox.tsx

@@ -214,9 +214,8 @@ export default function Toolbox({
               style={{
                 backgroundColor: preset.color,
                 borderColor: isSelected ? preset.color : 'transparent',
-                // @ts-ignore
                 '--tw-ring-color': preset.color,
-              }}
+              } as React.CSSProperties & { [key: string]: string }}
               title={preset.name}
             />
           );