Add OAuth flows and UI integration

- Implemented OAuth endpoints (providers list, authorization, callback, linked accounts management).
- Added UI translations for OAuth workflows (auth process messages, linked accounts management).
- Extended TypeScript types and React hooks to support OAuth features.
- Updated app configuration with OAuth-specific settings and provider details.
- Introduced skeleton implementations for authorization and token endpoints in provider mode.
- Included unit test and integration hooks for OAuth capabilities.

frontend/src/components/settings/index.ts

@@ -5,3 +5,4 @@ export { ProfileSettingsForm } from './ProfileSettingsForm';
 export { PasswordChangeForm } from './PasswordChangeForm';
 export { SessionCard } from './SessionCard';
 export { SessionsManager } from './SessionsManager';
+export { LinkedAccountsSettings } from './LinkedAccountsSettings';