Pin torchaudio==2.5.1+cu124 and add torch version diagnostic

The previous cu121 torchaudio linked against libcudart.so.13 which
doesn't exist on the ZeroGPU worker. Trying cu124 build of torchaudio
2.5.1 to match torch 2.5.1 preinstalled on ZeroGPU. Added diagnostic
print to confirm exact torch+CUDA versions in the logs.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app.py

@@ -15,6 +15,7 @@ from math import floor
 from pathlib import Path
 
 import torch
+print(f"[DIAG] torch={torch.__version__}  cuda={torch.version.cuda}")
 import numpy as np
 import soundfile as sf
 import ffmpeg

requirements.txt

@@ -16,5 +16,5 @@ spaces==0.48.1
 gradio==5.25.0
 pydantic==2.8.2
 av
---extra-index-url https://download.pytorch.org/whl/cu121
-torchaudio
+--extra-index-url https://download.pytorch.org/whl/cu124
+torchaudio==2.5.1+cu124