docs: add changelog entry

Author: KristjanESPERANTO

CHANGELOG.md

@@ -41,6 +41,7 @@ Thanks to: @dathbe.
   - Improve test reliability and maintainability
 - [tests] add alert module tests for different welcome_message configurations (#3867)
 - [lint-staged] use `prettier --write --ignore-unknown` in `lint-staged` to avoid errors on unsupported files (#3888)
+- [calendar] refactor: improve recurring event handling clarity and robustness (#3900)
 
 ### Updated