SignUp Memory Leak

## 📝 Issue Summary
Testing the develop branch, with commit 586bbb4445c2dc48519bef94e77d419cfe3417db, these classes leak:

SignupStepCompleteView,SignupStepViewModel

To reproduce it, quickly tap between these screens:
Landing→Sign-up→fill page1→다음→fill page2→다음→page3→Back→Landing (×3 cycles)

## ✅ TO - DO

- [ ] To-Do List

Start by checking out the develop branch at commit 586bbb4445c2dc48519bef94e77d419cfe3417db and reproduce the Landing → Sign-up flow, including three back-navigation cycles. Use the memory-leak report to inspect SignupStepCompleteView and SignupStepViewModel; the work is done when those classes no longer leak after the documented reproduction.

Written by the indexing model from the issue text.