Documentation Review for 4.1 Release

[jzheaux]

Review and update documentation for the 4.1 release:

• Review reference documentation for accuracy
• Update Prerequisites page similar to Spring Security's model (see https://docs.spring.io/spring-security/reference/prerequisites.html)
• Ensure all new features are documented
• Review and update README as needed
• Check for outdated information or broken links

This is part of the Spring LDAP 4.1 release preparation.

Related to #1125