fix: fixed card and address list having duplicate items, and a checkout flow infinate loop condition

api/handlers/addresses.go

@@ -141,6 +141,12 @@ func (h *AddressHandler) CreateAddress(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	// remove existing addres with the same street addres
+	var existing models.Address
+	if err := db.Where("user_id = ? AND street = ?", userID, address.Street).First(&existing).Error; err == nil {
+		db.Delete(&existing)
+	}
+
 	if err := db.Create(&address).Error; err != nil {
 		utils.RespondError(w, http.StatusInternalServerError, "DATABASE_ERROR", "failed to create address", nil)
 		return

api/handlers/cards.go

@@ -248,6 +248,13 @@ func (h *CardHandler) SaveCard(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	// remove existing local card with the same last4 + brand + expiry
+	var existingCard models.Card
+	if err := db.Where("user_id = ? AND last4 = ? AND brand = ? AND exp_month = ? AND exp_year = ?",
+		user.ID, pm.Card.Last4, string(pm.Card.Brand), pm.Card.ExpMonth, pm.Card.ExpYear).First(&existingCard).Error; err == nil {
+		db.Delete(&existingCard)
+	}
+
 	// Persist only the safe card metadata — no raw card data is stored.
 	card := models.Card{
 		UserID:          user.ID,