Fix Terraform type coercion in SMTP settings merge

Separate string and numeric settings into different locals to prevent
merge() from coercing integers to strings. The Supabase API requires
rate_limit_email_sent to be an integer.

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

terraform/modules/supabase/main.tf

@@ -207,19 +207,23 @@ locals {
     # require Team plan or higher - omitted to avoid 402 errors
   }
 
-  # Production-only SMTP settings (completely omitted for non-prod)
-  auth_smtp = var.is_production ? {
+  # Production-only SMTP string settings (completely omitted for non-prod)
+  auth_smtp_strings = var.is_production ? {
     smtp_admin_email = "team@send.sauci.app"
     smtp_host        = "smtp.resend.com"
-    smtp_max_frequency    = 1
     smtp_port        = "465"
     smtp_sender_name = "Sauci App"
     smtp_user        = "resend"
+  } : {}
+
+  # Production-only numeric settings (separate to preserve int type)
+  auth_smtp_numbers = var.is_production ? {
+    smtp_max_frequency    = 1
     rate_limit_email_sent = 25
   } : {}
 
   # Final merged auth config
-  auth_config = merge(local.auth_base, local.auth_smtp)
+  auth_config = merge(local.auth_base, local.auth_smtp_strings, local.auth_smtp_numbers)
 }
 
 resource "supabase_settings" "main" {