Fix 3 Code Review findings on FRE-4574

- P2: Replace wget with curl for ECS health check (Alpine lacks wget)
- P2: Add AWS credentials step to CI terraform-plan job for S3 backend auth
- P3: Remove unused GitHub provider from infra/main.tf

Co-Authored-By: Paperclip <noreply@paperclip.ing>

infra/modules/rds/main.tf

@@ -130,3 +130,9 @@ output "db_password_secret_arn" {
   description = "DB password secret ARN"
   value       = aws_secretsmanager_secret.db_password.arn
 }
+
+output "db_password" {
+  description = "Generated DB password"
+  value       = random_password.db_password.result
+  sensitive   = true
+}