Fix startup (remove --pre updates)

app.py

@@ -1,8 +1,5 @@
-import os
-# PyTorch 2.8 (temporary hack)
-os.system('pip install --upgrade --pre --extra-index-url https://download.pytorch.org/whl/nightly/cu126 "torch<2.9" spaces')
-
 # --- 1. Model Download and Setup (Diffusers Backend) ---
+import os
 import spaces
 import torch
 from diffusers import FlowMatchEulerDiscreteScheduler