Fix code scanning alert - Use of a broken or risky cryptographic algorithm

[houko]

Tracking issue for:

• https://github.com/houko/SpringBootUnity/security/code-scanning/4

[houko]

该告警已在 PR #44（fix: resolve all six CodeQL security alerts, 提交 0597a65）中修复：RandomUtil 里 token/密码/盐值的生成从可预测的 java.util.Random 改为 RandomStringUtils.secure()（由 SecureRandom 支撑）。CodeQL 复扫后该告警已标记为 fixed，关闭。