Upgrade project from Java 17 to Java 21

[Copilot]

This PR upgrades the entire project from Java 17 to Java 21 across all modules and CI/CD configurations.

Changes Made

Build Configuration Updates

• GitHub Actions CI/CD: Updated both test and detekt jobs to use JDK 21 with Temurin distribution
• Main App Module (app/build.gradle): Updated sourceCompatibility, targetCompatibility, and kotlinOptions.jvmTarget to version 21
• Data Repository Module (data/repository/build.gradle): Updated Java compatibility settings to version 21
• Domain UseCase Module (domain/usecase/build.gradle): Updated Java compatibility settings to version 21
• Domain Model Module (domain/model/build.gradle): Updated Java compatibility settings to version 21

Verification

All core functionality has been verified to work with JDK 21:

• ✅ Debug builds compile successfully
• ✅ Unit tests pass (all 12+ tests across modules)
• ✅ Static analysis (Detekt) passes without issues
• ✅ CI/CD pipeline updated to use JDK 21

Technical Details

The upgrade maintains full backward compatibility while leveraging the benefits of Java 21. All Android module configurations now consistently target JDK 21, ensuring uniform build behavior across the multi-module project structure.

The Kotlin compiler target has also been updated to JDK 21, maintaining compatibility with the latest Kotlin version (2.2.10) used in the project.

Testing

No functionality changes were made - this is purely a JDK version upgrade. The existing test suite validates that all business logic continues to work correctly with the new JDK version.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• esm.ubuntu.com
  • Triggering command: /usr/lib/apt/methods/https (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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