fix: 안읽음 카운트 Redis INCR 연산 직렬화 에러 해결 - #482

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4, actions/setup-java@v4, gradle/gradle-build-action@0d13054264b0bb894ded474f08ebb30921341cee. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

The `save-state` command is deprecated and will be disabled soon. Please upgrade to using Environment Files. For more information see: https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

Failed to restore v6-gradle|Linux|build[37a6259cc0c1dae299a7866489dff0bd]-c2df6e8160d30426f2ac728cf234e13855674fd3: Error: Cache service responded with 400

The `save-state` command is deprecated and will be disabled soon. Please upgrade to using Environment Files. For more information see: https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/