[Feat] Implement pull-to-refresh for the task list.

**Is your feature request related to a problem? Please describe.**
Currently, there is no quick way for users to refresh the task list to check for updates or sync changes. A pull-to-refresh gesture would make this process more intuitive and user-friendly.

**Describe the solution you'd like**
Enable a pull-to-refresh gesture for the task list.
When the user pulls down on the list, a refresh indicator (like a spinning loader) should appear.
Once the refresh is complete, the updated task list should be displayed.
Design specifications:
Use Flutter’s RefreshIndicator widget to implement this functionality.
The refresh gesture should provide visual feedback, such as a progress indicator.
If no changes are detected, notify the user with a subtle message like:
"You're all caught up!"

**Additional context**
Ensure the refresh behavior does not interfere with the current scroll functionality.

Start by locating the task list and reviewing how it currently loads or syncs tasks. Use Flutter's RefreshIndicator to provide pull-to-refresh feedback, display updated tasks when complete, preserve scrolling, and show "You're all caught up!" when there are no changes.

Written by the indexing model from the issue text.