TOD-5: Add optional due dates to todos

[claude]

Summary

• Added a date picker input next to the todo text field for setting an optional due date when creating a todo
• Due dates are stored in localStorage as part of each todo object (dueDate field, null if not set)
• Due date is displayed below the todo text in a smaller font
• Overdue items (past due date, not completed) are highlighted with a red background and red "Overdue:" label
• Todos are sorted by due date (earliest first), with undated todos appearing last

Linear Ticket

https://linear.app/issue/TOD-5

Closes TOD-5

🤖 Generated with Claude Code

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