[Enhancement] Add search and filter functionality for todos

[niat-web]

Feature Request

What:
Add the ability to search and filter todos
to help users find specific tasks quickly.

Expected behavior:

Search:

• Search bar at the top of the todo list
• Filters todos in real time as user types
• Searches by title and description
• Shows "No results found" when nothing matches

Filter buttons:

• All (shows all todos)
• Pending (shows only incomplete todos)
• Completed (shows only completed todos)

Counter:

• Show count next to each filter
  Example: "All (10) | Pending (7) | Completed (3)"

Why this is important:
When a user has many todos (20+), it becomes
very difficult to find a specific task.
Search and filter makes the app much more usable.

Technical implementation:

• Filter on frontend (no backend changes needed)
• Use React useState for search term and filter
• Filter the todos array before rendering

Acceptance Criteria:

• Search bar visible at top of todo list
• Todos filter in real time as user types
• All/Pending/Completed filter buttons work
• Count shown for each filter
• Empty state shown when no results