[Feat] Highlight Overdue Tasks in Red

**Is your feature request related to a problem? Please describe.**
Currently, overdue tasks are not visually distinguished from other tasks, making it harder for users to prioritize their attention on tasks that require immediate action.

**Describe the solution you'd like**
Modify the task list UI to highlight overdue tasks by displaying them in red text or adding a red border/background.
Automatically check task deadlines and apply the highlighting to tasks where the due date/time has passed.
Ensure that the highlighting updates dynamically as time progresses.

**Additional context**
Use Flutter’s DateTime.now() to compare the task’s deadline with the current time.

Start by locating the task list UI and the task data that contains each deadline; the issue names no files or tests. Check how the UI currently rebuilds as time passes, then verify that tasks past their deadlines are highlighted and that the highlighting changes as time progresses.

Written by the indexing model from the issue text.