Enhance product management and coupon features

- Added styling for input group add-ons and additional fields in SCSS.
- Updated shop coupon view to include a new column for usage count.
- Display coupon code and amount in order details if applicable.
- Improved product edit template to handle custom fields with required validation.
- Modified product save logic to include custom field requirements.
- Enhanced decimal normalization function for better input handling.
- Implemented checkbox normalization for form submissions.
- Updated custom fields in product templates to reflect required status.
- Fixed URL for fetching changelog updates.

admin/layout/style-scss/style.scss

@@ -2228,4 +2228,20 @@ textarea.form-control {
     width: 50px;
     text-align: center;
   }
+}
+
+.input-group-addon {
+  width: auto;
+
+  label {
+    display: flex;
+    align-items: center;
+    gap: 5px;
+  }
+}
+
+.additional_fields {
+  input[type="text"] {
+    height: 40px;
+  }
 }