Implement Go Backend Keycloak OIDC Client

Description

This issue focuses on implementing an OpenID Connect (OIDC) client in a Go backend to authenticate users via Keycloak. The integration will handle user redirection for login, receive/exchange authentication codes for tokens, and validate these tokens. This is essential for securing backend endpoints.

Acceptance Criteria

• Go app redirects to Keycloak for login successfully.

• OIDC callback processed upon successful Keycloak auth.

• Authorization code exchanged for OIDC tokens.

• ID token validated by Go backend.

• User claims extracted from ID token.

• Basic profile page displays extracted user info.

• Setup configurable via environment variables or file