feat: add JDK 25 image variants

[oshatrava]

Summary

• Add node20-jdk25, node22-jdk25, node24-jdk25 entries to versions/versions.json, pointing at the already-published ghcr.io/ringcentral-docker/node:*-jdk25 base image tags.
• Bump gradle_version to 9.7.1 for the new entries — Gradle 8.5 (used for the JDK17/21 tier) does not run under JDK 25, and early Gradle 9.x releases had a JDK 25 compatibility regression (Gradle 9.1.0+ says Java 25 is incompatible gradle/gradle#35062).
• Move is_latest from node22-jdk21 to node24-jdk25.
• No Dockerfile/scripts/CI changes needed — the build matrix and README table are generated from versions/versions.json automatically.

Verification

Local build of node24-jdk25 passed, confirming JDK 25.0.1 + Gradle 9.7.1 + Sonar Scanner 6.2.1.4610 + Maven all work together with no compatibility errors:

openjdk version "25.0.1" 2025-10-21 LTS
Gradle 9.7.1
SonarScanner CLI 6.2.1.4610 — Java 25.0.1 Eclipse Adoptium (64-bit)

Test plan

• Local docker build/docker run sanity check for node24-jdk25 (java/javac/mvn/gradle/sonar-scanner versions print cleanly)
• CI build matrix picks up the 3 new entries and pushes to Docker Hub + GHCR
• Trivy scan passes for the new images
• README auto-updates with the new rows after merge to master

Refs UIA-415009