Auth Regional Endpoint

Pre-login region probe for omicos-core (the Rust sidecar on the user's machine).

Returns the default cloud_base (auth.omicos.cn — the 备案 region, where most signups land) plus the full list of supported auth hosts. omicos-core hits this once at startup if it has no persisted config; after the user actually logs in, the auth response carries the user's home cloud_base (per their users.region) and the sidecar switches to that for everything downstream.

No auth required — the response is identical across users and leaks no PII; it's just service discovery.

Response shape (CN-only after the region consolidation): { "default_cloud_base": "https://auth.omicos.cn", "supported": ["https://auth.omicos.cn"] }