feat: HR Portal - Complete Multi-Tenant System with Redis Session Storage

Major Features:
- ✅ Multi-tenant architecture (tenant isolation)
- ✅ Employee CRUD with lifecycle management (onboarding/offboarding)
- ✅ Department tree structure with email domain management
- ✅ Company info management (single-record editing)
- ✅ System functions CRUD (permission management)
- ✅ Email account management (multi-account per employee)
- ✅ Keycloak SSO integration (auth.lab.taipei)
- ✅ Redis session storage (10.1.0.254:6379)
  - Solves Cookie 4KB limitation
  - Cross-system session sharing
  - Sliding expiration (8 hours)
  - Automatic token refresh

Technical Stack:
Backend:
- FastAPI + SQLAlchemy
- PostgreSQL 16 (10.1.0.20:5433)
- Keycloak Admin API integration
- Docker Mailserver integration (SSH)
- Alembic migrations

Frontend:
- Next.js 14 (App Router)
- NextAuth 4 with Keycloak Provider
- Redis session storage (ioredis)
- Tailwind CSS

Infrastructure:
- Redis 7 (10.1.0.254:6379) - Session + Cache
- Keycloak 26.1.0 (auth.lab.taipei)
- Docker Mailserver (10.1.0.254)

Architecture Highlights:
- Session管理由 Keycloak + Redis 統一控制
- 支援多系統 (HR/WebMail/Calendar/Drive/Office) 共享 session
- Token 自動刷新,異質服務整合
- 未來可無縫遷移到雲端

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

backend/tests/test_employees_api.py

@@ -0,0 +1,143 @@
+"""
+員工管理 API 測試 (6.2)
+測試 /api/v1/employees/ 的 CRUD 操作
+"""
+import datetime
+import pytest
+
+
+class TestEmployeeListAPI:
+    """員工列表 API 測試"""
+
+    def test_get_employees_empty(self, client):
+        """空資料庫回傳空列表"""
+        response = client.get("/api/v1/employees/")
+        assert response.status_code == 200
+        data = response.json()
+        assert data["total"] == 0
+        assert data["items"] == []
+
+    def test_get_employees_with_data(self, client, sample_employee):
+        """有資料時回傳員工列表"""
+        response = client.get("/api/v1/employees/")
+        assert response.status_code == 200
+        data = response.json()
+        assert data["total"] == 1
+        assert len(data["items"]) == 1
+        assert data["items"][0]["employee_id"] == "EMP001"
+
+    def test_get_employees_pagination(self, client, db, sample_business_unit):
+        """分頁功能測試"""
+        from app.models.employee import Employee
+        # 建立 5 個員工
+        for i in range(5):
+            emp = Employee(
+                tenant_id=1,
+                employee_id=f"EMP00{i+1}",
+                username_base=f"user{i+1}",
+                legal_name=f"員工{i+1}",
+                hire_date=datetime.date.today(),
+                status="active",
+            )
+            db.add(emp)
+        db.commit()
+
+        # 取第 1 頁，每頁 2 筆
+        response = client.get("/api/v1/employees/?page=1&page_size=2")
+        assert response.status_code == 200
+        data = response.json()
+        assert data["total"] == 5
+        assert len(data["items"]) == 2
+        assert data["total_pages"] == 3
+
+
+class TestEmployeeCreateAPI:
+    """員工建立 API 測試"""
+
+    def test_create_employee_success(self, client, sample_business_unit):
+        """成功建立員工"""
+        payload = {
+            "username_base": "porsche.chen",
+            "legal_name": "陳保時",
+            "english_name": "Porsche Chen",
+            "hire_date": str(datetime.date.today()),
+            "business_unit_id": sample_business_unit.id,
+            "job_title": "軟體工程師",
+            "job_level": "Mid",
+            "email_quota_mb": 5120,
+        }
+        response = client.post("/api/v1/employees/", json=payload)
+        assert response.status_code == 201
+        data = response.json()
+        assert data["username_base"] == "porsche.chen"
+        assert data["legal_name"] == "陳保時"
+        assert data["status"] == "active"
+        assert "employee_id" in data  # 自動產生
+
+    def test_create_employee_duplicate_username(self, client, sample_employee, sample_business_unit):
+        """重複帳號名稱應回傳 400"""
+        payload = {
+            "username_base": "test.user",  # 與 sample_employee 相同
+            "legal_name": "另一個用戶",
+            "hire_date": str(datetime.date.today()),
+            "business_unit_id": sample_business_unit.id,
+            "job_title": "工程師",
+            "job_level": "Junior",
+            "email_quota_mb": 1024,
+        }
+        response = client.post("/api/v1/employees/", json=payload)
+        assert response.status_code in [400, 409, 422]
+
+    def test_create_employee_missing_required_fields(self, client):
+        """缺少必填欄位應回傳 422"""
+        response = client.post("/api/v1/employees/", json={"username_base": "only.this"})
+        assert response.status_code == 422
+
+
+class TestEmployeeDetailAPI:
+    """員工詳情 API 測試"""
+
+    def test_get_employee_success(self, client, sample_employee):
+        """成功取得員工詳情"""
+        response = client.get(f"/api/v1/employees/{sample_employee.id}")
+        assert response.status_code == 200
+        data = response.json()
+        assert data["id"] == sample_employee.id
+        assert data["employee_id"] == "EMP001"
+
+    def test_get_employee_not_found(self, client):
+        """不存在的員工 ID 應回傳 404"""
+        response = client.get("/api/v1/employees/99999")
+        assert response.status_code == 404
+
+    def test_update_employee_success(self, client, sample_employee):
+        """成功更新員工資料"""
+        payload = {"legal_name": "更新後姓名", "phone": "02-12345678"}
+        response = client.put(f"/api/v1/employees/{sample_employee.id}", json=payload)
+        assert response.status_code == 200
+        data = response.json()
+        assert data["legal_name"] == "更新後姓名"
+        assert data["phone"] == "02-12345678"
+
+    def test_delete_employee_success(self, client, sample_employee):
+        """成功刪除 (停用) 員工"""
+        response = client.delete(f"/api/v1/employees/{sample_employee.id}")
+        assert response.status_code == 200
+
+
+class TestEmployeeSearchAPI:
+    """員工搜尋 API 測試"""
+
+    def test_search_by_name(self, client, sample_employee):
+        """依姓名搜尋"""
+        response = client.get("/api/v1/employees/?search=測試")
+        assert response.status_code == 200
+        data = response.json()
+        assert data["total"] >= 1
+
+    def test_filter_by_status(self, client, sample_employee):
+        """依狀態篩選"""
+        response = client.get("/api/v1/employees/?status=active")
+        assert response.status_code == 200
+        data = response.json()
+        assert all(item["status"] == "active" for item in data["items"])