Increase ZeroGPU duration to 720s for local testing

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

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

app.py

@@ -398,7 +398,7 @@ else:
 
 
 
-@spaces.GPU(duration=120)
+@spaces.GPU(duration=720)
 def generate_qr_code_unified(
     prompt: str,
     text_input: str,