Fix model loading 404 errors and improve time estimation

Model Loading Fixes:
- Add fallback loading when model_index.json returns 404
- Try alternative paths (diffusers/, diffusion_model/, pipeline/)
- Try generic DiffusionPipeline as fallback
- Check HuggingFace API for actual file structure
- Load from subdirectories if model_index.json found there
- Apply same fallback to I2V image model loading

Time Estimation Improvements:
- Add hardware detection (GPU model, VRAM, RAM, CPU cores)
- Detect GPU tier (extreme/high/medium/low/very_low)
- Calculate realistic time estimates based on GPU performance
- Account for VRAM constraints and offloading penalty
- Consider distributed/multi-GPU setups
- More accurate model loading times (minutes, not seconds)
- Account for resolution impact (quadratic relationship)
- Add 20% overhead for memory management
- Print hardware info for transparency

GPU Tier Performance Multipliers:
- Extreme (RTX 4090, A100, H100): 1.0x
- High (RTX 4080, RTX 3090, V100): 1.5x
- Medium (RTX 4070, RTX 3080, T4): 2.5x
- Low (RTX 3060, RTX 2070): 4.0x
- Very Low (GTX 1060, etc.): 8.0x