**Signup flow does not use unified auth routing**

### 🐛 Describe the bug

#### Description
```md
### Bug
signup() directly calls setUserProfileData() instead of isUserLoggedIn().

This bypasses:
- onboarding routing
- report checks
- navigation consistency

### Expected Behavior
Signup should behave the same as login after session creation.

### Actual Behavior
Signup partially initializes auth state.

### Fix
Replace setUserProfileData() with isUserLoggedIn() in signup().