Add localStorage persistence to Todo app

[vishal-singh-web]

• Added src/hooks/useLocalStorage.js — reusable hook for JSON persistence to localStorage.
• Refactored Home.jsx to use the hook (removed inline localStorage logic).
• Normalized todo input (trim + case-insensitive duplicate prevention).
• Fixed in-place array mutation in moveUp/moveDown (now clone + swap).
• Replaced add control with semantic .
• Todos now persist order and data across reloads.

Closes #175