fix: lazy-initialize Resend client to avoid missing API key error at build time

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/lib/resend.ts

@@ -3,7 +3,12 @@ import { render } from '@react-email/components'
 import { LeadAlertEmail } from '@/emails/LeadAlert'
 import { logger } from '@/lib/logger'
 
-const resend = new Resend(process.env['RESEND_API_KEY'])
+function getResend() {
+  const key = process.env['RESEND_API_KEY']
+  if (!key) return null
+  return new Resend(key)
+}
+
 const FROM = process.env['RESEND_FROM'] ?? 'noreply@shumiland.ua'
 const MANAGER_EMAILS = (process.env['MANAGER_EMAILS'] ?? '').split(',').filter(Boolean)
 
@@ -28,6 +33,12 @@ export async function sendLeadAlert(lead: LeadAlertData): Promise<void> {
     })
   )
 
+  const resend = getResend()
+  if (!resend) {
+    logger.warn('RESEND_API_KEY not configured — skipping email alert')
+    return
+  }
+
   try {
     await resend.emails.send({
       from: FROM,