Fix ZeroGPU quota duration ceiling

app.py

@@ -149,8 +149,12 @@ print("[startup] pipeline ready. HeartMuLa/HeartCodec weights load on first gene
 
 # ---------------------------------------------------------------- GPU function
 def _allocation_duration(lyrics: str, tags: str, duration_sec: float) -> int:
-    """Declared ZeroGPU runtime ceiling (quota is billed on actual runtime)."""
-    return 120 + int(duration_sec) * 2
+    """Declared ZeroGPU runtime ceiling (quota is billed on actual runtime).
+
+    Cap at 295s: a free account with exactly 300s left rejects requests of
+    300s (e.g. duration_sec=90 -> 120 + 90*2 = 300).
+    """
+    return min(295, 120 + int(duration_sec) * 2)
 
 
 @spaces.GPU(duration=_allocation_duration)