Add persistent focus timer and improve task management

[binduhasini11]

Related Issue

Closes #138

Summary

Implemented persistent Pomodoro timer recovery so active focus sessions continue correctly after page refreshes or accidental reloads.

Changes Made

• Added localStorage support for Pomodoro timer state
• Saved timer progress, duration, and running state
• Restored timer automatically on page refresh
• Recalculated elapsed time using timestamps for accurate recovery
• Added cleanup of stored timer state on reset/completion

Testing

• Started timer and refreshed page to verify persistence
• Tested pause and resume functionality
• Verified timer resets correctly
• Confirmed completed sessions clear saved state
• Tested multiple refreshes during active countdown

Screenshots

timerPersistsOnRefresh.mp4

Before Refresh:

After Refresh:

Checklist

• Code follows project style
• Tested locally
• No unrelated changes included
• Documentation updated (if applicable)