Feature: Employee Performance Analytics Dashboard

## 📌 Summary

Add a **Performance Analytics Dashboard** to visualize key employee metrics such as productivity, department growth, retention, and turnover. The dashboard will provide managers and HR teams with **actionable insights** beyond the current CRUD and simple stats.

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## 🎯 Motivation

Right now, the system provides only **basic CRUD** for employees/departments and some visualizations. Real-world enterprises need **analytics** to drive decisions:

* Which departments are growing fastest?
* Which employees are high performers?
* What’s the monthly hiring vs attrition trend?

This feature will make the app a **data-driven management tool** instead of just a record keeper.

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## ✅ Acceptance Criteria

* [ ] New backend endpoints under `/api/analytics` to expose aggregated data:

* Employee count by department
* New hires per month
* Turnover rate per quarter
* Average tenure
* [ ] Frontend charts (using `react-chartjs-2`) to visualize:

* Line chart: employee growth over time
* Pie chart: employees by department
* Bar chart: hires vs exits
* [ ] Dashboard page restricted to **Managers** and **HR** roles (ties in with RBAC).
* [ ] Unit & integration tests for new backend endpoints.
* [ ] Ensure responsiveness and dark mode support.

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## 🚀 Implementation Notes

* **Backend (Spring Boot)**

* Use `Spring Data JPA` aggregate queries (`COUNT`, `GROUP BY`, `DATE_TRUNC`) for stats.
* Add `AnalyticsController.java` to expose REST endpoints.

* **Frontend (React)**

* Create `AnalyticsDashboard.js` component.
* Fetch data via `axios` from `/api/analytics/*`.
* Display in a grid layout with charts and KPI cards.

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## 🔒 Security

* Endpoints should check user role before returning sensitive analytics.
* Ensure no PII (e.g., salary, personal details) is leaked unless explicitly allowed.

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