chore(gateway-contracts): fix vulnerabilities in docker image (#278)

Author: melanciani

gateway-contracts/Dockerfile

@@ -1,4 +1,4 @@
-FROM ghcr.io/zama-ai/fhevm-node:latest
+FROM ghcr.io/zama-ai/fhevm/gci/nodejs:22.14.0-alpine3.21
 
 WORKDIR /app
 
@@ -29,4 +29,8 @@ RUN npx hardhat clean && \
 
 USER fhevm:fhevm
 
+# Check that some pre-compiled contracts are present
+HEALTHCHECK --interval=30s --timeout=5s --start-period=5s --retries=3 \
+    CMD test -d /app/artifacts && find /app/artifacts -type f -name "*.json" | grep -q . || exit 1
+
 ENTRYPOINT ["/bin/bash", "-c"]