Merge pull request #29 from darbyluv2code/feature/update-java-26-to-27

Update Java version from 26 to 27

Merge pull request #28 from darbyluv2code/feature/update-java-25-to-26

Update Java version from 25 to 26 across all course projects

Java 25 Baseline

This release establishes Java 25 as the baseline for all design pattern examples.

Key changes:
- All 21 Maven projects now compile with Java 25
- Fixed class name/filename mismatches in observer patterns
- Added GitHub Actions parallel build workflow (3 jobs, ~36 second build time)
- Added build status badge to README

Build Status: All 21 projects compile successfully
Sections: Creational (5), Structural (5), Behavioral (11)

Update Spring Boot REST APIs course title in README (#4)