fix: use multi-arch index digest for eclipse-temurin:25-jre runtime stage (#225)

## Summary

- The `eclipse-temurin:25-jre` digest pinned in the runtime stage
(`5742cdb9`) was a linux/amd64 single-platform manifest, not the OCI
image index
- This caused arm64 multi-arch builds to fail with `Invalid ELF image
for this architecture` under QEMU emulation
- Replaced with the image index digest (`671061ae`) so both amd64 and
arm64 builds resolve the correct platform manifest

Author: coopernetes

Dockerfile

@@ -56,7 +56,7 @@ RUN sed -i \
     git-proxy-java-dashboard/build/install/git-proxy-java-dashboard/bin/git-proxy-java-dashboard
 
 # ── Runtime stage ─────────────────────────────────────────────────────────────
-FROM docker.io/eclipse-temurin:25-jre@sha256:5742cdb98ef117621ad75f57475ab127db04f344d9c523307cc60b9955bdd676
+FROM docker.io/eclipse-temurin:25-jre@sha256:671061ae5a8f0d6827816e15bc39d21e224c43ff96998a97cd0d3989c4d17815
 
 WORKDIR /app