(WIP) feat: oauth2 && sso

[seefs001]

Summary by CodeRabbit

• New Features
  • Full OAuth2/OIDC server: token/authorize/introspect/revoke/userinfo, discovery and JWKS endpoints, key rotation/import/generation, token revocation and storage.
• Admin UI
  • OAuth2 settings panel, JWKS manager, server/JWKS viewers, OAuth client management (CRUD, one-time secrets, regenerate).
• UX
  • User consent page, PKCE demo pages, example Go test client, new modals and responsive modal component.
• Auth
  • Optional OAuth JWT/Bearer middleware with scope checks and revocation enforcement.
• Chores
  • Added OAuth/JWT dependencies and DB migration for OAuth clients.