chore(backend): bump Dockerfile.jvm OpenJDK 21 UBI base image tag 1.20 → 1.24

[hugomelendez]

Problem / need

The backend container image pins outdated Red Hat UBI9 OpenJDK 21 base tags (1.21) in backend/Dockerfile.jvm. Quarkus 3.x and the current RH OpenJDK container stream use tag 1.24. Staying on 1.21 misses platform updates and diverges from Quarkus defaults.

Proposed solution

Update both FROM lines in backend/Dockerfile.jvm:

• registry.access.redhat.com/ubi9/openjdk-21:1.21 → registry.access.redhat.com/ubi9/openjdk-21:1.24
• registry.access.redhat.com/ubi9/openjdk-21-runtime:1.21 → registry.access.redhat.com/ubi9/openjdk-21-runtime:1.24

Verify:

• CI Build and push to Quay succeeds on the PR
• Optional local: podman build -f backend/Dockerfile.jvm backend/
• Backend starts and serves API (smoke via compose or Helm)

Suggested milestone

Backlog

Impacted repos

• gateforge