Ecommerce Feature Integration Needed

I’m ready to turn my existing site into a fully-functional store. The core pieces I need you to build are:

• Product catalog – I want visitors to browse a clean, searchable list of items.
• Shopping cart – users must be able to add, remove, and update quantities seamlessly across pages.
• Payment gateway – secure checkout with industry-standard options such as Stripe or PayPal, plus the ability to expand later.

My site is already live; your job is to integrate these three components, match the current design, and test end-to-end so orders flow through without errors. Please set things up so I can add or edit products myself afterward from an admin panel.

Acceptance criteria
• Catalog loads quickly and displays products with images, price, and description.
• Cart persists between pages and calculates totals accurately, including shipping and tax rules we define.
• Payment gateway processes real transactions in live mode and sends confirmation emails to both the customer and me.
• No console errors, mobile-responsive on major breakpoints, and SSL enforced during checkout.

Let me know which platform or stack you recommend (e.g., WooCommerce, custom PHP/MySQL, or another mainstream framework) and provide a timeline for initial rollout plus a round of refinements after launch.