feat: Add OAuth 2.0 / OIDC SSO login support

- Add OAuth SSO type definitions (OAuthSSOProvider, OAuthSSOConfig, IOAuthLink)
- Add oauthSSO field to SystemConfig for provider configuration
- Update IUser interface to support OAuth-linked accounts
- Create OAuth SSO service with provider management and token exchange
- Add SSO controller with login initiation and callback handling
- Update frontend login page with SSO provider buttons
- Add SSOCallbackPage for handling OAuth redirects
- Update database entities and DAOs for OAuth link storage
- Add i18n translations for SSO-related UI elements
- Add comprehensive unit tests for OAuth SSO service

Co-authored-by: samanhappy <2755122+samanhappy@users.noreply.github.com>

src/db/entities/SystemConfig.ts

@@ -30,6 +30,9 @@ export class SystemConfig {
   @Column({ type: 'simple-json', nullable: true })
   oauthServer?: Record<string, any>;
 
+  @Column({ type: 'simple-json', nullable: true })
+  oauthSSO?: Record<string, any>;
+
   @Column({ type: 'boolean', nullable: true })
   enableSessionRebuild?: boolean;