Send branded HTML emails and harden SMTP2GO webhooks.

Fix campaign stuck on sending under async queue, and stop UUID ValidationError when SMTP2GO tests send "Headers Unavailable".

site/public/templates/emails/contact_email.txt

@@ -0,0 +1,17 @@
+New contact form inquiry — {{ brand_name|default:"Monica Dhillon" }}
+
+Name: {{ name }}
+Email: {{ email }}
+Phone: {{ phone }}
+Address:
+{{ address }}
+
+Message:
+{{ message }}
+
+{% if portal_url %}View in portal: {{ portal_url }}
+{% endif %}
+—
+{{ brand_name|default:"Monica Dhillon" }}
+{{ site_url|default:"https://mkdrealtor.com" }}
+{% if brand_tagline %}{{ brand_tagline }}{% endif %}