feat: Add ATS score history chart

[Atharv094]

📝 Description

This PR implements a visual line chart to track a user's ATS score

history over their past analyses.
It uses recharts to plot the score vs. date, helping logged-in
users visually track their improvement. The chart gracefully handles
empty/single-entry states by only rendering when the user has at least
2 analysis entries, and it's easily accessible directly from the
account/history sidebar.

## 🔗 Related Issue

Closes #378

## ✅ Type of Change

- [ ] 🐞 Bug fix (non-breaking change that fixes an issue)
- [x] ✨ New feature (non-breaking change that adds functionality)
- [ ] 📚 Documentation update
- [x] 💅 UI/UX improvement
- [ ] ♻️ Refactor (no functional change)
- [ ] ⚡ Performance improvement

## 🧪 How Has This Been Tested?

- [x] Frontend builds (`npm run build`) and lints (`npm run lint`)

clean
- [ ] Backend tests pass (python manage.py test analyzer)
- [x] Manually tested in the browser / API client

📋 Checklist

- [x] My code follows the project's style and conventions
- [x] I have linked the related issue above
- [x] I have read the [Code of Conduct](CODE_OF_CONDUCT.md)

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