Add Mailketing API support to send-notification function

The send-notification function was using SMTP by default and failing with
ConnectionRefused errors. Added Mailketing API integration to match the
email provider used by other functions (send-auth-otp, send-email-v2).

Changes:
- Added sendViaMailketing() function with form-encoded body
- Added "mailketing" case to provider switch (now the default)
- Changed default provider from "smtp" to "mailketing"
- Reads API token from mailketing_api_token or api_token settings

This ensures order_created emails are sent successfully via Mailketing
just like other email notifications in the system.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

supabase/functions/send-notification/index.ts

@@ -33,6 +33,36 @@ interface EmailPayload {
   from_email: string;
 }
 
+// Send via Mailketing API
+async function sendViaMailketing(payload: EmailPayload, apiToken: string): Promise<void> {
+  const params = new URLSearchParams();
+  params.append('api_token', apiToken);
+  params.append('from_name', payload.from_name);
+  params.append('from_email', payload.from_email);
+  params.append('recipient', payload.to);
+  params.append('subject', payload.subject);
+  params.append('content', payload.html);
+
+  console.log(`Sending email via Mailketing to ${payload.to}`);
+
+  const response = await fetch('https://api.mailketing.co.id/api/v1/send', {
+    method: 'POST',
+    headers: {
+      'Content-Type': 'application/x-www-form-urlencoded',
+    },
+    body: params.toString(),
+  });
+
+  if (!response.ok) {
+    const errorText = await response.text();
+    console.error('Mailketing API error:', response.status, errorText);
+    throw new Error(`Mailketing API error: ${response.status} ${errorText}`);
+  }
+
+  const result = await response.json();
+  console.log('Mailketing API response:', result);
+}
+
 // Send via SMTP
 async function sendViaSMTP(payload: EmailPayload, config: SMTPConfig): Promise<void> {
   const boundary = "----=_Part_" + Math.random().toString(36).substr(2, 9);
@@ -284,10 +314,16 @@ serve(async (req: Request): Promise<Response> => {
     };
 
     // Determine provider and send
-    const provider = settings.integration_email_provider || "smtp";
+    const provider = settings.integration_email_provider || "mailketing";
     console.log(`Sending email via ${provider} to ${recipient_email}`);
 
     switch (provider) {
+      case "mailketing":
+        const mailketingToken = settings.mailketing_api_token || settings.api_token;
+        if (!mailketingToken) throw new Error("Mailketing API token not configured");
+        await sendViaMailketing(emailPayload, mailketingToken);
+        break;
+
       case "smtp":
         await sendViaSMTP(emailPayload, {
           host: settings.smtp_host,