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/kms-key/README.md

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+# kms-key
+
+KMS Key Module
+
+## Usage
+
+```hcl
+module "kms_key" {
+  source = "../modules/kms-key"
+  
+  # Required variables
+  name = ""
+
+  # Optional: see variables.tf for all options
+}
+```
+
+## Requirements
+
+| Name | Version |
+|------|---------|
+| terraform | >= 1.5.0 |
+| aws | >= 5.0 |
+
+## Inputs
+
+| Name | Description | Type | Required |
+|------|-------------|------|----------|
+| name | Key name (used for alias) | `string` | yes |
+| description | Key description | `string` | no |
+| deletion_window_in_days | Waiting period before key deletion (7-30 days) | `number` | no |
+| enable_key_rotation | Enable automatic key rotation (annual) | `bool` | no |
+| multi_region | Create a multi-region key | `bool` | no |
+| key_usage | Key usage: ENCRYPT_DECRYPT or SIGN_VERIFY | `string` | no |
+| key_spec | Key spec (SYMMETRIC_DEFAULT, RSA_2048, ECC_NIST_P256, etc.) | `string` | no |
+| admin_principals | IAM ARNs with full admin access to the key | `list(string)` | no |
+| user_principals | IAM ARNs with encrypt/decrypt access | `list(string)` | no |
+| service_principals | AWS service principals that can use the key (e.g., logs.amaz... | `list(string)` | no |
+| grant_accounts | Account IDs with cross-account access | `list(string)` | no |
+| tags |  | `map(string)` | no |
+
+## Outputs
+
+| Name | Description |
+|------|-------------|
+| key_id | KMS key ID |
+| key_arn | KMS key ARN |
+| alias_arn | KMS alias ARN |
+| alias_name | KMS alias name |
+| key_policy | Key policy document |
+
+## License
+
+Apache 2.0 - See LICENSE for details.