Add refresh token rotation in AuthModule.

src/auth/auth.service.ts

@@ -1,8 +1,13 @@
-export class AuthModule {
+export class AuthModule {
   /** JWT authentication service — matches Halite component path. */
   validateAccessToken(token: string): boolean {
     if (!token) return false;
     const parts = token.split(".");
     return parts.length === 3;
   }
+
+  /** Ticket #42 — refresh token rotation (demo change for invalidation). */
+  rotateRefreshToken(oldToken: string): string {
+    return `rotated:${oldToken}`;
+  }
 }