- modernize UI with tailwind dark mode support

- add circular progress indicator for timer
- implement settings modal with customizable timer durations
- add sound and browser notifications
- create task tracking with estimated/used pomodoros
- add session tracking with goal setting
- implement auto-start breaks option
- add keyboard shortcuts (space, r, 1-3)
- store settings and tasks in localStorage for persistence
- add task statistics (completed/remaining/total)

Author: TobiasMue91