[DOCKER-SWARM] Implement Docker Swarm Translation Engine with Orchestration Features

[chutch3]

🐝 Docker Swarm Translation Engine Implementation

This PR implements Issue #38 - a comprehensive Docker Swarm translation engine that converts homelab.yaml to Docker Swarm stack format with full orchestration features.

✅ 100% Test Coverage - All 26/26 Tests Passing

🚀 Core Features Implemented

Swarm Orchestration Features

• ✅ Service Placement Constraints - Convert deployment strategies to Swarm constraints
• ✅ Service Scaling & Replicas - Support for multi-replica services
• ✅ Health Checks & Auto-Restart - HTTP health check endpoints with automatic restart
• ✅ Resource Limits & Reservations - Memory limits and reservations for services
• ✅ Overlay Networks - Cross-node service discovery and communication
• ✅ Secrets Management - Docker Swarm secrets for sensitive data
• ✅ Rolling Updates - Zero-downtime deployment configuration

Deployment Strategy Translation

# homelab.yaml → Docker Swarm constraints
deploy: driver     → node.hostname == driver
deploy: all        → mode: global (run on every node)  
deploy: node-01    → node.hostname == node-01
deploy: random/any → mode: replicated (Swarm scheduler)

Advanced Features

• ✅ Bash-based YAML parsing (no yq dependency per user request)
• ✅ Custom network support with overlay driver
• ✅ Environment variable handling
• ✅ Volume management with driver configuration
• ✅ Service enablement filtering (excludes disabled services)

🔧 Technical Implementation

Translation Engine

• Script: scripts/translate_homelab_to_swarm.sh
• Input: homelab.yaml with deployment: docker_swarm
• Output: Valid Docker Swarm stack YAML
• Dependencies: Pure bash (no external YAML parsers)

CLI Integration

# Generate Swarm stack
./selfhosted.sh generate-swarm

# Validate generated stack  
./scripts/translate_homelab_to_swarm.sh validate-stack docker-stack.yaml

Example Translation

# Input (homelab.yaml)
services:
  web-app:
    image: nginx:alpine
    port: 80
    deploy: any
    replicas: 3
    health_check: /health

# Output (docker-stack.yaml) 
services:
  web-app:
    image: nginx:alpine
    ports:
      - "80:80"
    deploy:
      mode: replicated
      replicas: 3
      restart_policy:
        condition: unless-stopped
      update_config:
        parallelism: 1
        delay: 10s
    healthcheck:
      test: ["CMD", "curl", "-f", "http://localhost:80/health"]
      interval: 30s
      timeout: 10s
      retries: 3
    networks:
      - overlay_network

🧪 Comprehensive Testing

Test Coverage

• 26/26 tests passing (100% success rate)
• Core functionality: Service translation, deployment strategies
• Advanced features: Health checks, secrets, custom networks
• Edge cases: Disabled services, machine assignment, validation

Test Categories

• ✅ YAML validation and syntax checking
• ✅ Service property translation (image, port, storage, environment)
• ✅ All deployment strategies (driver, all, specific, random, any)
• ✅ Swarm orchestration features (scaling, health checks, secrets)
• ✅ Network configuration (overlay networks, custom networks)
• ✅ Error handling and edge cases

📋 TDD Workflow Completed

🔴 RED Phase

• Created 26 comprehensive failing tests
• Defined expected behavior for all Swarm features

🟢 GREEN Phase

• Implemented bash-based YAML parsing functions
• Built complete Swarm translation engine
• All 26 tests now passing

🔵 REFACTOR Phase

• Cleaned up code structure and removed unused variables
• Fixed shellcheck warnings and linting issues
• Ensured clean YAML output without log message contamination

🔗 Related Work

This complements the existing Docker Compose implementation:

• Issue [DOCKER-COMPOSE] Implement Basic Translation Engine #35: Docker Compose Translation Engine ✅ Complete
• Issue [DOCKER-COMPOSE] Implement Per-Machine Nginx Configuration #36: Nginx Distribution for Docker Compose ✅ Complete
• Issue [DOCKER-COMPOSE] Implement Multi-Machine Deployment Coordination #37: SSH-based Deployment Engine ✅ Complete
• Issue [DOCKER-SWARM] Implement Translation Engine with Orchestration Features #38: Docker Swarm Translation Engine ✅ This PR

🎯 Ready for Production

• ✅ All tests passing
• ✅ No external dependencies
• ✅ Clean, maintainable code
• ✅ Comprehensive error handling
• ✅ Full Swarm orchestration support

This implementation provides a solid foundation for Docker Swarm deployments with intelligent service orchestration and zero-downtime updates. 🚀