feat: Terraform Foundation - AWS Landing Zone

Enterprise-grade multi-tenant AWS cloud foundation.

Modules:
- GitHub OIDC for keyless CI/CD authentication
- IAM account settings and security baseline
- AWS Config Rules for compliance
- ABAC (Attribute-Based Access Control)
- SCPs (Service Control Policies)

Features:
- Multi-account architecture
- Cost optimization patterns
- Security best practices
- Comprehensive documentation

Tech: Terraform, AWS Organizations, IAM Identity Center

terraform/modules/tenant-budget/README.md

@@ -0,0 +1,38 @@
+# tenant-budget
+
+Terraform module for AWS landing zone pattern.
+
+Create tenant-specific AWS budget alerts.
+
+## Planned Features
+
+- [ ] Monthly budget with configurable limit
+- [ ] Multi-threshold alerts (50%, 80%, 100%, 120%)
+- [ ] Cost allocation tag filtering
+- [ ] SNS and email notifications
+- [ ] Forecasted spend alerts
+- [ ] Auto-actions at budget limits (optional)
+
+## Planned Usage
+
+```hcl
+module "tenant_budget" {
+  source = "../modules/tenant-budget"
+  
+  tenant_name  = "acme-corp"
+  budget_limit = 500
+  
+  alert_thresholds = [50, 80, 100]
+  
+  notification_emails = [
+    "billing@acme.com",
+    "admin@acme.com"
+  ]
+  
+  cost_filter_tags = {
+    Tenant = "acme-corp"
+  }
+  
+  enable_forecasted_alerts = true
+}
+```