Banned users can still use the API

Banned users can still use the API: a task in MiMo-V2.6-RL-oss: Agentic RL Environments (MiMo RL release). We use the :banned role to lock abusive users out of the site, but it looks like the API doesn't honour it. Steps to reproduce: 1. Pick a user with an existing API key and give them the…