* refactor: replace loggedInUsersTz with timeZone in busy-times API - Add new timeZone parameter to CalendarBusyTimesInput - Mark loggedInUsersTz as deprecated - Update getBusyTimes endpoint to prioritize timeZone parameter - Maintain backward compatibility with loggedInUsersTz - Add validation to ensure at least one timezone parameter is provided - Update API documentation with new parameter example Fixes #25423 * fix: improve timezone validation in CalendarBusyTimesInput - Use custom ValidatorConstraint instead of problematic ValidateIf - Properly validate that at least one timezone parameter is provided - Improve code quality and clarity * fix: update DTOs for getBusyTimes * cleanup * fix: abstract normalize timezone logic into platform types util function * chore: update e2e tests * fixup * fixup --------- Co-authored-by: Ryukemeister <sahalrajiv6900@gmail.com> Co-authored-by: Rajiv Sahal <sahalrajiv-extc@atharvacoe.ac.in>