Retail E-Commerce Site Setup

I want a straightforward online retail store that lets me list physical products, manage a small inventory, and accept orders smoothly. I’m not interested in Shopify, WooCommerce, or Magento; instead, I need a lightweight custom build on my own hosting so I remain fully in control of the code and data.

Scope (keep it lean and clean):
• Basic homepage, product-listing page, product-detail page, cart, and checkout.
• Simple admin panel to add, edit, and deactivate products, adjust stock, and view orders.
• Payment gateway integration with at least one popular provider (for example Razorpay or PayPal) plus cash-on-delivery toggle.
• Mobile-responsive layout with fast load times.
• Initial on-page SEO setup (meta titles, descriptions, and clean URLs).

I just need the core store working—no complex automations or marketing add-ons for now. Hand-over should include all source files, a short setup guide, and a quick walkthrough so I can maintain the site myself.