⚡ Bolt: Execute independent email requests concurrently via Promise.all

[Snigdh41]

What: Replaced sequential email sending via the Resend API with concurrent requests using Promise.all.
Why: The notification email to the admin and the auto-reply to the user are completely independent. Waiting for the first to finish before starting the second unnecessarily increases the Cloudflare Worker's execution time.
Impact: Reduces the latency of the contact API endpoint, halving the time spent on external email API calls.
Measurement: Measure the total execution time of the /contact endpoint before and after the change; observing the [contact] ✅ All emails sent successfully log timestamp should show a marked reduction in overall request latency.

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PR created automatically by Jules for task 14528154017234022619 started by @Snigdh41

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