[Enhancement] Add todo completion statistics on dashboard

[niat-web]

Feature Request

What:
Show a statistics section at the top of the
dashboard showing the user's todo progress.

Expected behavior:
Show 3 stat cards at top of page:

• Total Todos: 10
• Completed: 3 ✅
• Pending: 7 ⏳

Also show a simple progress bar:
"30% Complete"

Why this is important:
Users can quickly see their overall progress
and feel motivated to complete more tasks.

Technical implementation:

• Calculate stats from existing todos array
• No backend changes needed
• Simple math: completed/total * 100

Acceptance Criteria:

• 3 stat cards visible on dashboard
• Stats update when todos are added/completed/deleted
• Progress bar shows completion percentage
• Looks clean and matches existing design