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/acm-certificate/README.md

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+# acm-certificate
+
+ACM Certificate Module
+
+## Usage
+
+```hcl
+module "acm_certificate" {
+  source = "../modules/acm-certificate"
+  
+  # Required variables
+  domain_name = ""
+
+  # Optional: see variables.tf for all options
+}
+```
+
+## Requirements
+
+| Name | Version |
+|------|---------|
+| terraform | >= 1.5.0 |
+| aws | >= 5.0 |
+
+## Inputs
+
+| Name | Description | Type | Required |
+|------|-------------|------|----------|
+| domain_name | Primary domain name for the certificate | `string` | yes |
+| subject_alternative_names | Additional domain names (SANs) for the certificate | `list(string)` | no |
+| zone_id | Route53 zone ID for DNS validation (null for email validatio... | `string` | no |
+| validation_method | Validation method: DNS or EMAIL | `string` | no |
+| wait_for_validation | Wait for certificate validation to complete | `bool` | no |
+| validation_timeout | Timeout for certificate validation | `string` | no |
+| tags |  | `map(string)` | no |
+
+## Outputs
+
+| Name | Description |
+|------|-------------|
+| certificate_arn | ARN of the certificate |
+| certificate_domain_name | Primary domain name |
+| certificate_status | Certificate status |
+| validation_records |  |
+| validated_certificate_arn | ARN of the validated certificate |
+
+## License
+
+Apache 2.0 - See LICENSE for details.