Immutable Infrastructure with Packer

Help me implement immutable infrastructure using Packer.

Requirements:
- Cloud provider: [AWS/GCP/Azure/VMware]
- Base OS: [Ubuntu/Amazon Linux/CentOS/Windows]
- Application stack: [describe software to install]
- Image distribution: [regions, accounts]

Packer configuration:
1. Image building
   - Base image selection
   - Provisioners (shell, Ansible, Chef)
   - Post-processors
   - Variable management

2. Image hardening
   - CIS benchmark compliance
   - Security patches
   - Unnecessary service removal
   - Audit configuration

3. CI/CD integration
   - Automated builds on code change
   - Image testing
   - Image promotion workflow
   - Version management

4. Image management
   - Tagging strategy
   - Image lifecycle (deprecation, deletion)
   - AMI sharing (AWS)
   - Image scanning

Include:
- Packer template (HCL2)
- Provisioner scripts
- CI/CD pipeline
- Image management automation