Pin PyTorch <2.4.0 for AudioCraft compatibility

AudioCraft requires PyTorch 2.1.x. PyTorch 2.4+ changed the
torch.utils._pytree API (serialized_type_name parameter), breaking
AudioCraft's model loading.

- Pin torch>=2.1.0,<2.4.0
- Pin torchaudio>=2.1.0,<2.4.0
- Remove broken pytree monkey-patch attempt

After pulling, reinstall with:
  pip install -r requirements.txt --force-reinstall torch torchaudio

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

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

requirements.txt

@@ -1,6 +1,6 @@
-# Core ML
-torch>=2.1.0
-torchaudio>=2.1.0
+# Core ML - Pin to AudioCraft-compatible versions (2.4+ breaks pytree API)
+torch>=2.1.0,<2.4.0
+torchaudio>=2.1.0,<2.4.0
 audiocraft>=1.3.0
 xformers>=0.0.22