fix(app/product): users can always change colors

This patch updates the frontend to allow users to always change the
selected color. If their currently selected size is not available in a
color, selecting that color will simply select the first size option.

app/routes/_wardrobe.products.$product/variants.tsx

@@ -42,7 +42,7 @@ function Colors() {
               key={color}
               label={color}
               prices={variantsWithColor.flatMap((v) => v.prices)}
-              variant={active}
+              variant={active ?? variantsWithColor[0]}
             />
           )
         })}