Fix: Contact Form

The contact form at route `/contact` (uigrades.vercel.app/contact) uses Sendgrid, which is no longer supporting a free tier for emailing services. Research and implement a way to send emails using a different (and free) emailing service.

Start at the `/contact` route/handler and find where submissions are processed and SendGrid is invoked. Next, trace the SendGrid configuration and environment usage, then replace that provider integration with a free email service in the same flow and update related config/docs. Verify success by running the app and submitting the `/contact` form, then confirm delivery works and this path no longer depends on SendGrid.

Written by the indexing model from the issue text.