Style: Unify cart Continue Shopping button with wishlist style

Updated cart dropdown Continue Shopping buttons to use btn-outline
class (matching wishlist style) instead of btn-text across all pages.

Changes:
- shop.html: btn-text → btn-outline
- contact.html: btn-text → btn-outline
- product.html: btn-text → btn-outline
- about.html: btn-text → btn-outline

All cart Continue Shopping buttons now have consistent styling
with the wishlist Continue Shopping button (purple outline style).

website/public/shop.html

@@ -684,7 +684,7 @@
                   <a href="/checkout" class="btn-primary-full"
                     >Proceed to Checkout</a
                   >
-                  <a href="/shop" class="btn-text">Continue Shopping</a>
+                  <a href="/shop" class="btn-outline">Continue Shopping</a>
                 </div>
               </div>
             </div>