fix: ensure Dockerfile ends with a newline and maintain EXPOSE directive

Author: Peter Nguyen

backend/Dockerfile

@@ -47,4 +47,4 @@ COPY --from=builder --chown=chaos:rust /backend/server/target/release/server /ba
 USER rust
 
 ENTRYPOINT ["/backend/server"]
-EXPOSE 8080
+EXPOSE 8080