Show discount code and final price on product page (storefront display for Advanced Discount Codes)

User story: As a merchant, I want to display under each product price a message like "Get this product for $XXXXX by using coupon code HEYBEAUTIFUL" so shoppers immediately see the final price if they use the code at checkout.

Acceptance criteria:

• Admin can pick an existing Advanced Discount Code campaign and associate it with a product, variant, or collection for storefront display.

• The storefront widget displays the discount code text, the calculated final price for the current variant (original price, discounted price, and savings), and a copy-to-clipboard action for the code.

• The widget appears directly below the product price on product pages and updates per variant selection.

• The widget respects campaign schedule and module eligibility (only shows when the product/variant is eligible and campaign is active).

• The widget does NOT auto-apply the discount; it only displays the code and final price preview.

• Admin can customize visibility, text, and style (placement, color, font) and preview before publishing.

Notes/fallbacks:

• If final price cannot be reliably calculated (complex combination rules, exclusions, or missing variant info), show the code with a tooltip: "Final price shown at checkout."