Sign in with Google or any OpenID Connect provider, including multiple providers

Operators can now configure Google and any generic OpenID Connect (OIDC) identity provider on the same Hive instance, and Hive will display a dedicated login option for each one. Google mode uses HIVE_GOOGLE_CLIENT_ID / HIVE_GOOGLE_CLIENT_SECRET and supports an optional HIVE_GOOGLE_ALLOWED_DOMAINS allowlist (with Google’s hd= hint when a single domain is set). The generic OIDC path is configured with HIVE_OIDC_ISSUER, HIVE_OIDC_CLIENT_ID, HIVE_OIDC_CLIENT_SECRET, an optional HIVE_OIDC_DISPLAY_NAME that labels the login button, and an optional HIVE_OIDC_ALLOWED_DOMAINS allowlist. Callbacks land at /auth/google/callback and /auth/oidc/callback on the deployed host. Provider login buttons also render on public instances so administrators can always sign in.