feat: add template for email

apps/api/templates/emails/test-email.html

@@ -0,0 +1,14 @@
+<!doctype html>
+<html>
+  <head>
+    <meta charset="utf-8">
+    <title>Test email from {{venueName}}</title>
+  </head>
+  <body>
+    <p>Hi {{customerName}},</p>
+    <p>This is a test email from {{venueName}} to verify that email reminders are working correctly.</p>
+    <p>If you received this, the email configuration is working!</p>
+    <hr>
+    <p style="color: #888; font-size: 12px;">This is a test — no action needed.</p>
+  </body>
+</html>