feat(auth): capture roles and restaurant details on registration

[gTanusri]

Issue Link

Closes #140

Changes Made

• Added role selection to the registration page using active roles loaded from the backend.
• Added restaurant name, description, and phone number fields to signup with client-side validation.
• Extended user registration payload to accept selected role IDs and restaurant details.
• Created restaurant records during user registration inside the existing transactional registration flow.
• Allowed public GET access to role endpoints so the registration page can populate the role list before login.

Type of Change

• New feature
• Bug fix
• Documentation update
• Code refactor

Testing Performed

Frontend Testing

• Production build passes with npm run build
• Role and restaurant fields validate before submission

Backend Testing

• Backend compile passes with ./gradlew.bat compileJava
• Full backend test suite passes