101 feature add support for compose project env variable

[Ketbome]

Description

Implementa soporte opcional para COMPOSE_PROJECT en backend para que los contenedores Minecraft usen prefijo de proyecto (<COMPOSE_PROJECT>_<serverId>) en lugar de depender de container_name fijo en mc.
Se mantiene retrocompatibilidad para servidores existentes mediante fallback de resolución de contenedor.

También se agregó alias de red estable (serverId) en modo proxy para no romper resolución de mc-router.

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📝 Documentation update
• 🔧 Configuration change
• ♻️ Refactoring (no functional changes)
• 🧪 Tests

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• I have tested my changes locally
• I have updated documentation if needed
• My changes don't introduce new warnings or errors

Screenshots (if applicable)

N/A (no UI changes)

Related Issues

Closes #