Pin JUnit BOM to 5.13.4 to restore integration test discovery in CI

[Copilot]

Description

The referenced GitHub Actions run failed in :craftrelay-integration-tests:integrationTest during JUnit discovery with a NoSuchMethodError in JUnit Platform internals. This change restores a compatible JUnit/JUnit Platform set for the existing Testcontainers-based test stack.

Changes

• Dependency alignment

  • Updated gradle/libs.versions.toml:
    • junit = "6.1.2" → junit = "5.13.4"
  • This re-aligns junit-jupiter, junit-platform-launcher, and junit-platform-commons to compatible 5.x/1.13.x versions used by current modules.

• Minimal scope

  • No production code or test logic changes.
  • Single-file dependency version correction only.

# gradle/libs.versions.toml
-junit = "6.1.2"
+junit = "5.13.4"

Testing

• Ran targeted module test:
  • ./gradlew :craftrelay-api:test --no-configuration-cache
• Verified resolved runtime alignment via dependency insight:
  • org.junit.platform:junit-platform-commons resolves to 1.13.4
  • org.junit.jupiter:junit-jupiter-engine resolves to an aligned Jupiter/Platform set

Checklist

• Code builds successfully
• Tests pass
• Documentation updated (if needed)
• I confirm that I have personally reviewed all changes in this Pull Request and take responsibility for their correctness, regardless of whether AI tools were used.

AI Disclosure

• This Pull Request was created without AI assistance.
• This Pull Request includes AI-assisted code or documentation.