Fix: AttributeError total_mem -> total_memory in system monitor

- torch.cuda.get_device_properties() returns SimpleNamespace with .total_memory (not .total_mem)
- Fixes crash when opening System Monitor tab

app.py

@@ -1383,7 +1383,7 @@ def get_system_info() -> dict:
         "torch_version": torch.__version__,
         "cuda_available": torch.cuda.is_available(),
         "gpu_name": torch.cuda.get_device_name(0) if torch.cuda.is_available() else "N/A",
-        "gpu_memory_total": f"{torch.cuda.get_device_properties(0).total_mem / 1024**3:.1f} GB" if torch.cuda.is_available() else "N/A",
+        "gpu_memory_total": f"{torch.cuda.get_device_properties(0).total_memory / 1024**3:.1f} GB" if torch.cuda.is_available() else "N/A",
         "gpu_memory_allocated": f"{torch.cuda.memory_allocated() / 1024**3:.2f} GB" if torch.cuda.is_available() else "N/A",
         "gpu_memory_reserved": f"{torch.cuda.memory_reserved() / 1024**3:.2f} GB" if torch.cuda.is_available() else "N/A",
         "is_zero_gpu": IS_ZERO_GPU,