Implement Email Notifications Replit

My web app is already live on Replit, with the domain served through AWS Route 53. I now need reliable email notifications wired in so users receive messages straight from the site.

Here’s the current stack and what I expect from you:
• Code is hosted and deployed inside Replit.
• I would like to send the emails through the Resend API, which is available in Replit’s Secrets/Environment manager.
• Only email notifications are required for now; SMS or push can stay out of scope until a later phase.

Your task is to add the emailing layer, hook it cleanly into the existing codebase, and verify that outgoing messages reach real inboxes (Gmail, Outlook, etc.) without landing in spam. You may suggest or create the necessary templates, set up SPF/DKIM or any DNS records on AWS if Resend needs them, and document the small set of environment variables I’ll have to keep updated.

The end-deliverable is a working branch merged back into the main project, plus short deployment notes so I can reproduce the setup in future repls.