feat: add G1GC heap uncommit flags so container memory shrinks after uploads

-XX:MinHeapFreeRatio=10 -XX:MaxHeapFreeRatio=20 -XX:G1HeapUncommitPercent=5
After large game uploads, the JVM committed heap stays high. These flags tell
G1GC to release free heap pages back to the OS after GC cycles, so Docker
memory usage drops back toward baseline instead of staying at peak.

Dockerfile

@@ -25,4 +25,4 @@ COPY --from=build /build/target/quarkus-app/ /app/
 EXPOSE 8765
 VOLUME /data
 ENV DOSTALGIA_DATA_DIR=/data
-ENTRYPOINT ["java", "-jar", "quarkus-run.jar"]
+ENTRYPOINT ["java", "-XX:+UseG1GC", "-XX:MinHeapFreeRatio=10", "-XX:MaxHeapFreeRatio=20", "-XX:G1HeapUncommitPercent=5", "-jar", "quarkus-run.jar"]