Coupon not applied with existing active cart

It didn’t work consistently, even with an empty cart, so I added a forced cart save to make it work whether the cart is empty or contains items. It might not be the most elegant solution, but it seems to work well.

I’ve made some updates to my changes. Essentially, I added logic that mimics the coupon submission process without relying on the temp store. It’s working, but I’m unsure if this is a good way to handle it.