fix(core): close CallableStatement in DerbySnapshotOperation to prevent JDBC resource leak

[daguimu]

Problem

In DerbySnapshotOperation.doDerbyBackup(), the CallableStatement is created inside a try-with-resources block that only manages the Connection. The statement itself is never closed, causing a JDBC resource leak on each Derby snapshot backup operation.

Root Cause

The CallableStatement was created as a local variable inside the try block rather than being declared in the try-with-resources header:

try (Connection holder = ...) {
    CallableStatement cs = holder.prepareCall(backupSql);  // not auto-closed
    cs.setString(1, backupDirectory);
    cs.execute();
}

While closing the Connection may implicitly close associated statements in some JDBC drivers, the JDBC specification does not guarantee this behavior, and relying on it is a resource management anti-pattern.

Fix

• Moved the CallableStatement declaration into the try-with-resources header so it is automatically closed after use, consistent with JDBC best practices.

Tests Added

Change Point	Test
CallableStatement now auto-closed via try-with-resources	testOnSnapshotSaveWithMocks() — added verify(callableStatement).close() to confirm the statement is properly closed after backup execution

Impact

Only affects Derby embedded database backup operations. No behavioral change — backups work identically, but the CallableStatement is now properly closed after each use.

[github-actions]

Thanks for your this PR. 🙏
Please check again for your PR changes whether contains any usage/api/configuration change such as Add new API , Add new configuration, Change default value of configuration.
If so, please add or update documents(markdown type) in docs/next/ for repository nacos-group/nacos-group.github.io

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感谢您提交的PR。 🙏
请再次查看您的PR内容，确认是否包含任何使用方式/API/配置参数的变更，如：新增API、新增配置参数、修改默认配置等操作。
如果是，请确保在提交之前，在仓库nacos-group/nacos-group.github.io中的docs/next/目录下添加或更新文档（markdown格式）。