fix(backend): use Depends(get_current_user) for node preferences route to fix 422 error; improve frontend error reporting in apiClient

Hardening OIDC Auth: Resolve discovery deadlocks, implement identity sync, fix session persistence, and stabilize voice chat initialization

Refactor AI Config and Fix Login failure: Migrated services to a structured api directory, updated backend schemas for multiple TTS/STT providers, and improved settings/chat UI coverage.