Fix issue #11: Add comprehensive multi-GPU support

[LifeJiggy]

• Add multi_gpu_support.py with device_map and DataParallel support
• Implement automatic GPU distribution for component placement
• Add gradient checkpointing and xFormers memory efficient attention
• Include automatic mixed precision (AMP) for performance
• Provide readiness checks and usage examples

Addresses the question 'Is there a plan to support multiple GPUs?' with
full implementation supporting dual GPUs and beyond for faster inference."