Migrate E-Commerce Site to Square

I need help moving my entire Lovable online store from its current platform to Square. The store holds about 1,700 products—1,200 of them already sync live with eBay, each item carrying multiple photos and, in many cases, short videos. All images sit safely in Cloudflare, and the site is running smoothly right now, so downtime must be kept to an absolute minimum.

Here is the flow I’m aiming for:

• Products, photos, videos, and the existing eBay link have to be the first assets live on Square.
• Square will become the single source of truth for inventory; every stock change on Square should automatically update eBay.
• The full customer email list and newsletter need to move over as well, then continue to send from within Square’s marketing tools.

If Square’s native email limits become an issue, I’m open to your suggestions for retaining the same newsletter frequency without losing deliverability, but my preference is to keep everything under one roof.

Please outline your approach for data export/import, how you will maintain URL integrity (for SEO), and the approximate timeline you’ll need to complete each milestone.