feat: add spring-boot-auth-roles module with custom login and role-based access

[rohan-gouda27]

This PR introduces a new module, spring-boot-auth-roles, under the spring-boot-security-root project. The module demonstrates a simple Spring Boot application with:

• Custom login page using Thymeleaf
• Role-based access control with three pages:
  • Index page: Public, accessible by anyone, with login/logout button
  • User page: Accessible by authenticated users with USER or ADMIN role
  • Admin page: Accessible by authenticated users with ADMIN role
• In-memory user management configured via application.yaml
• Spring Security configuration using SecurityFilterChain
• Thymeleaf templates for all pages
• Example users:
  • user / password (USER role)
  • admin / password (ADMIN, USER roles)

This module is intended as a reference for integrating Spring Security, Thymeleaf, and role-based authentication in a modern Spring Boot application.

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Closes: #