Fix import errors and NumPy compatibility

- Rename create_theme() to create_audiocraft_theme() to match imports
- Add missing get_custom_css() function
- Pin numpy<2.0.0 for PyTorch compatibility
- Replace deprecated pynvml with nvidia-ml-py

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

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

src/ui/theme.py

@@ -3,7 +3,7 @@
 import gradio as gr
 
 
-def create_theme() -> gr.themes.Base:
+def create_audiocraft_theme() -> gr.themes.Base:
     """Create custom theme for AudioCraft Studio.
 
     Returns:
@@ -301,3 +301,12 @@ CUSTOM_CSS = """
     }
 }
 """
+
+
+def get_custom_css() -> str:
+    """Get custom CSS for additional styling.
+
+    Returns:
+        CSS string
+    """
+    return CUSTOM_CSS