Update GPU quota information and add Zero GPU error guidance

Enhanced the main description with detailed GPU quota information including image size specifications and added helpful guidance for users encountering Zero GPU errors.

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

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

app.py

@@ -2794,10 +2794,15 @@ if __name__ == "__main__" and not os.environ.get("QR_TESTING_MODE"):
         **Privacy:** Generated images auto-delete after 1 hour. Download promptly!
 
         **GPU Quota:**
-        - **Unauthenticated**: 120s daily (~6 artistic generations)
-        - **Authenticated**: 210s daily (~10 artistic generations)
+        - **Unauthenticated**: 120s daily (~1 generation at 1024px or ~6 at 512px)
+        - **Authenticated**: 210s daily (~10 artistic generations at 512px)
         - **Tip**: Use Standard pipeline (2x faster) to save quota
 
+        **Zero GPU Error?** If you see "Zero GPU" error, you've run out of quota. Options:
+        - Wait until tomorrow for quota reset
+        - Register a Hugging Face account for more generations
+        - Subscribe to PRO for even more generations
+
         Choose a tab below to get started!
         """)