Add accounts and auth_states tables with models and tests
Install @adonisjs/auth and @atproto/oauth-client-node packages.
Create SQLite migrations for accounts (DID-keyed, stores OAuth
session data) and auth_states (temporary OAuth flow state storage).
Add corresponding Lucid models following existing conventions.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>