Sign in with Google or any OIDC provider from a redesigned login page

Hive now supports one OIDC provider per instance through a unified HIVE_OIDC_* configuration. Set HIVE_OIDC_PROVIDER to google and supply your Google OAuth client ID and secret, or set it to generic and provide your OIDC issuer, client ID, and secret. The login page shows the matching button automatically, includes a “Continue without signing in” link on public instances, and was redesigned to match the tuist style. You can also restrict access to allowed email domains. The flow uses Ueberauth and ueberauth_oidcc for standard discovery, PKCE, and token exchange.