fix: Docker EXPOSE 改为仅 6401，entrypoint 添加 -Duser.timezone

审查发现：
- EXPOSE 6400 误导用户映射后端端口，实际只需 6401（反向代理）
- TZ 环境变量不如 JVM -Duser.timezone 可靠

Dockerfile

@@ -16,7 +16,7 @@ RUN unzip netdisk-fast-download-bin.zip && \
 COPY ./docker-entrypoint.sh /docker-entrypoint.sh
 RUN chmod +x /docker-entrypoint.sh
 
-EXPOSE 6400 6401
+EXPOSE 6401
 
 RUN addgroup --system appgroup && adduser --system --ingroup appgroup appuser
 ENTRYPOINT ["/docker-entrypoint.sh"]

docker-entrypoint.sh

@@ -6,4 +6,4 @@ chown -R appuser:appgroup /app/db /app/logs /app/resources 2>/dev/null || true
 
 # Run Java directly - entrypoint is PID 1, exec makes Java PID 1
 # Docker SIGTERM goes directly to Java, triggering ShutdownHook
-exec java -Xmx${JVM_XMX:-512M} ${JVM_OPTS} -jar /app/netdisk-fast-download.jar
+exec java -Xmx${JVM_XMX:-512M} ${JVM_OPTS} -Duser.timezone=${TZ:-Asia/Shanghai} -jar /app/netdisk-fast-download.jar