Update CHANGELOG.md with recent changes

Add entries for changes since version 16.1.0 release:
- Bug fix for React Server Components manifest file resolution (#1818)
- Documentation for monorepo merger plan (#1817)
- Improved server bundle security test coverage (#1815)

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Co-Authored-By: Claude <noreply@anthropic.com>

Author: justin808

CHANGELOG.md

@@ -23,6 +23,18 @@ After a release, please make sure to run `bundle exec rake update_changelog`. Th
 
 Changes since the last non-beta release.
 
+#### Bug Fixes
+
+- **React Server Components**: Fixed bug in resolving `react-server-client-manifest.json` file path. The manifest file path is now correctly resolved using `bundle_js_file_path` for improved configuration flexibility and consistency in bundle management. [PR 1818](https://github.com/shakacode/react_on_rails/pull/1818) by [AbanoubGhadban](https://github.com/AbanoubGhadban)
+
+#### Documentation
+
+- **Monorepo merger plan**: Added comprehensive documentation for merging React on Rails repositories into a monorepo structure. This plan outlines the strategy for consolidating the main gem, Pro features, and tutorial repositories while preserving history and maintaining development workflows. [PR 1817](https://github.com/shakacode/react_on_rails/pull/1817) by [AbanoubGhadban](https://github.com/AbanoubGhadban)
+
+#### Code Improvements
+
+- **Test coverage**: Significantly improved server bundle security test coverage with comprehensive tests for `enforce_private_server_bundles` configuration. Added parametrized tests for bundle path resolution covering all file existence combinations and enhanced security enforcement tests for both server bundles and RSC bundles. Also fixed misleading comments in the codebase. [PR 1815](https://github.com/shakacode/react_on_rails/pull/1815) by [AbanoubGhadban](https://github.com/AbanoubGhadban)
+
 ### [16.1.0] - 2025-09-23
 
 #### New Features