Add analysis history tab to store past results

Amitesh-Currently the app shows only the latest analysis result. Add a History tab that keeps a list of past analyses in memory during the session.

Each history entry should show:

• Timestamp
• Input type (text/file/QR)
• Risk level badge (LOW/MEDIUM/HIGH/CRITICAL)
• Short summary

Clicking an entry should expand and show the full result card.

Files to modify: frontend/app/page.tsx, frontend/components/