Fix GPUMemoryManager param and simplify theme

- Fix comfyui_reserve_bytes -> comfyui_reserve_gb in main.py
- Simplify Gradio theme to avoid invalid parameters

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

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

main.py

@@ -44,7 +44,7 @@ async def initialize_services():
     logger.info("Initializing GPU manager...")
     gpu_manager = GPUMemoryManager(
         device_id=0,
-        comfyui_reserve_bytes=int(settings.comfyui_reserve_gb * 1024**3),
+        comfyui_reserve_gb=settings.comfyui_reserve_gb,
     )
 
     # Initialize model registry