Bump bitsandbytes to 0.49.2 for CUDA 13.0 support

0.47.0 has no precompiled binary for CUDA 13.0 (only up to 12.9), so it
failed to load its native library at import time on this Space's
cu130 torch build, and the int8 text_encoder load fell back to bf16
(gracefully, per app.py's own fallback). CUDA 13.0 binaries were added
starting in bitsandbytes 0.48.0.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

requirements.txt

@@ -2,7 +2,7 @@ accelerate==1.14.0
 diffusers==0.39.0
 peft==0.19.1
 transformers==4.57.1
-bitsandbytes==0.47.0
+bitsandbytes==0.49.2
 huggingface_hub
 pyarrow
 sentencepiece