change gpu duration calculation to dynamically adapt to the number of inference steps

This will increase the allocated ZeroGPU for a run according to the amount of steps, and reduce the amount of `ZeroGPU worker error GPU Task Aborted` errors

app.py

@@ -125,14 +125,7 @@ def get_duration(image,
                  seed,
                  progress):
     """Calculate dynamic GPU duration based on parameters."""
-    if duration_seconds >= 3:
-        return 220
-    elif sampling_steps > 35 and duration_seconds >= 2:
-        return 180
-    elif sampling_steps < 35 or duration_seconds < 2:
-        return 105
-    else:
-        return 90
+    return sampling_steps * 15
 
 # --- 2. Gradio Inference Function ---
 @spaces.GPU(duration=get_duration)