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>

main.py

@@ -16,17 +16,6 @@ os.chdir(PROJECT_ROOT)
 # Add project root to path
 sys.path.insert(0, str(PROJECT_ROOT))
 
-# PyTorch 2.5+ compatibility patch for audiocraft
-# The _pytree API changed - add backwards compatibility
-try:
-    import torch.utils._pytree as _pytree
-    if not hasattr(_pytree, 'register_pytree_node') and hasattr(_pytree, '_register_pytree_node'):
-        _pytree.register_pytree_node = _pytree._register_pytree_node
-    elif not hasattr(_pytree, '_register_pytree_node') and hasattr(_pytree, 'register_pytree_node'):
-        _pytree._register_pytree_node = _pytree.register_pytree_node
-except Exception:
-    pass  # Ignore if patch fails
-
 from config.settings import get_settings
 from src.core.gpu_manager import GPUMemoryManager
 from src.core.model_registry import ModelRegistry

requirements.txt

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