Update an existing user.

Updatable Fields:

• role_id: User's role ID (must match an ID from GET /roles)
• email: Email address (must be globally unique across all accounts)
• first_name: User's first name
• last_name: User's last name
• phone: Phone number
• user_avatar: Avatar URL

Lifecycle Management:

• To deactivate a user, use the POST /users/{id}/deactivate endpoint
• To delete a user, use the DELETE /users/{id} endpoint
• The active field cannot be set via PATCH - use dedicated endpoints