infra: size the VPC connector (min/max_instances) for provider v6

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: SociableSteve

infra/redis.tf

@@ -14,5 +14,8 @@ resource "google_vpc_access_connector" "conn" {
   region        = var.region
   network       = "default"
   ip_cidr_range = "10.8.0.0/28"
+  # Newer provider requires explicit sizing (instances-based here).
+  min_instances = 2
+  max_instances = 3
   depends_on    = [google_project_service.svc]
 }