Support for replication mode

[atimin]

Closes #

Please check if the PR fulfills these requirements

• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)
• CHANGELOG.md has been updated (for bug fixes / features / docs)

What kind of change does this PR introduce?

Feature

What was changed?

• Add replication mode support (enabled/paused/disabled) to the C++ client, including parsing/serialization and mode-only PATCH updates.
• Extend replication API tests to cover mode handling and default to enabled, keeping existing settings intact when toggling.
• Document the new capability in the changelog.

Related issues

reductstore/reductstore#1065

Does this PR introduce a breaking change?

No

Other information: