Improve Ui and Functionality of Focus Timer

The current Focus Time feature is minimal and limited:

• Timer is fixed at 25 minutes with no option for custom durations.
• UI is basic and lacks engaging visuals.

Proposed Improvements:

• Custom Timer: Allow users to set any focus duration.
• Enhanced UI:
  • Clear and attractive timer display
  • Progress visualization (circular bar/animations)
  • Intuitive start/pause/reset buttons
• Optional Features:
  • Display task name
  • Sound/visual notification when time ends
  • Light/dark theme support

Benefit: Makes Focus Time flexible, visually appealing, and more motivating for users.