Independent Time Zone Support for Consistent Scheduling Across Time Zones

Implement an "Independent Time Zone" feature in Akiflow to keep tasks and slots at their scheduled local times, regardless of time zone changes.

Currently, tasks/slots in Akiflow are tied to the time zone they were created in, requiring manual rescheduling when traveling. The proposed feature will ensure that a 9 AM task/slot remains at 9 AM in any time zone. This is important for fixed routines that are not tied to time zones, but to the individual schedules.The current setup makes sense for events (calls, meetings) and tied team tasks, but not for personal tasks and slots.