feat(packages): add standalone auth and payment

packages/auth/src/telegram/auth.service.ts

@@ -114,6 +114,11 @@ export class AuthService {
     });
   }
 
+  /** Accept a session returned by credentials or an external provider. */
+  acceptSession(session: AuthSession): void {
+    this.activateSession(session);
+  }
+
   private activateSession(session: AuthSession): void {
     this.sessionSignal.set(session);
     this.statusSignal.set('authenticated');