fix: Upgrade accelerate to 0.26.1 for low_cpu_mem_usage support

**Critical Fix:**
- accelerate: 0.25.0 → 0.26.1 (minimum required for low_cpu_mem_usage)
- Fixes: Using low_cpu_mem_usage=True requires accelerate>=0.26.0

**Error Resolved:**
All models were failing to load with:
'Using low_cpu_mem_usage=True requires Accelerate: pip install accelerate>=0.26.0'

This was blocking:
- microsoft/DialoGPT-small
- gpt2
- beomi/llama-2-ko-7b
- All other models

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

requirements.txt

@@ -2,4 +2,4 @@ gradio==5.9.1
 transformers==4.46.0
 torch==2.1.0
 safetensors==0.4.5
-accelerate==0.25.0
+accelerate==0.26.1