🐳 Add Docker ECR Deployment Workflow

[TheOrangePuff]

Summary

• Multi-platform Docker builds 🏗️ - Build for linux/amd64, linux/arm64, and ARM variants
• ECR integration 📦 - Push images to existing ECR repositories
• Container signing ✍️ - Optional cosign-based image signing and attestation
• Smart tagging 🏷️ - Multiple strategies: latest, semantic, branch, custom
• Build optimization ⚡ - Advanced caching with registry and inline cache support

Streamlined Docker deployment pipeline with multi-platform support and optimization features for containerized applications.

Important: The ECR repository must exist before running this workflow - the workflow will fail if the repository doesn't exist.

Usage examples:

# Basic usage
uses: aligent/workflows/.github/workflows/docker-ecr-deploy.yml@main
with:
  ecr-repository: my-app
secrets:
  aws-access-key-id: ${{ secrets.AWS_ACCESS_KEY_ID }}
  aws-secret-access-key: ${{ secrets.AWS_SECRET_ACCESS_KEY }}

# Production with signing
uses: aligent/workflows/.github/workflows/docker-ecr-deploy.yml@main
with:
  ecr-repository: my-app
  tag-strategy: "semantic"
  enable-signing: true
secrets:
  aws-access-key-id: ${{ secrets.AWS_ACCESS_KEY_ID }}
  aws-secret-access-key: ${{ secrets.AWS_SECRET_ACCESS_KEY }}
  container-signing-key: ${{ secrets.COSIGN_PRIVATE_KEY }}