Update bundled Gradle to 9.7.1

[cdsap]

Summary

• update the bundled Gradle default from 9.7.0 to 9.7.1
• regenerate bundled Gradle wrapper resources with the project update script
• refresh README CLI/default/example Gradle references

Validation

• ./gradlew :project-generator:unitTest --tests io.github.cdsap.projectgenerator.model.GradleTest --tests io.github.cdsap.projectgenerator.writer.GradleWrapperTest --tests io.github.cdsap.projectgenerator.SupportedGradleVersionsE2ETest
• ./gradlew :project-generator:unitTest
• ./gradlew :cli:test