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/conftest.py

@@ -0,0 +1,124 @@
+"""
+pytest 共用 Fixtures
+提供測試用的資料庫 Session、測試客戶端等
+"""
+import sys
+import os
+from pathlib import Path
+
+# 確保 backend 根目錄在 Python path 中
+sys.path.insert(0, str(Path(__file__).parent.parent))
+
+# 在導入任何 app 模組前，先將 PostgreSQL JSONB 替換為 JSON (SQLite 相容)
+from sqlalchemy.dialects.postgresql import JSONB
+from sqlalchemy import JSON
+import sqlalchemy.dialects.postgresql as pg_dialect
+pg_dialect.JSONB = JSON
+
+import pytest
+from fastapi.testclient import TestClient
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+from sqlalchemy.pool import StaticPool
+
+from app.db.base import Base
+from app.db.session import get_db
+from app.main import app
+
+# ============================================================
+# 測試資料庫 (使用 SQLite in-memory)
+# ============================================================
+SQLALCHEMY_DATABASE_URL = "sqlite://"
+
+engine = create_engine(
+    SQLALCHEMY_DATABASE_URL,
+    connect_args={"check_same_thread": False},
+    poolclass=StaticPool,
+)
+TestingSessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+
+@pytest.fixture(scope="function")
+def db():
+    """提供測試用的資料庫 Session (每個測試獨立)"""
+    Base.metadata.create_all(bind=engine)
+    session = TestingSessionLocal()
+    try:
+        yield session
+    finally:
+        session.close()
+        Base.metadata.drop_all(bind=engine)
+
+
+@pytest.fixture(scope="function")
+def client(db):
+    """提供測試用的 FastAPI TestClient"""
+    def override_get_db():
+        try:
+            yield db
+        finally:
+            pass
+
+    app.dependency_overrides[get_db] = override_get_db
+    with TestClient(app) as c:
+        yield c
+    app.dependency_overrides.clear()
+
+
+# ============================================================
+# 測試資料 Fixtures
+# ============================================================
+
+@pytest.fixture
+def sample_business_unit(db):
+    """建立測試用事業部"""
+    from app.models.business_unit import BusinessUnit
+    bu = BusinessUnit(
+        tenant_id=1,
+        name="智能研發服務事業部",
+        code="SMART",
+        email_domain="lab.taipei",
+        description="測試事業部",
+        is_active=True,
+    )
+    db.add(bu)
+    db.commit()
+    db.refresh(bu)
+    return bu
+
+
+@pytest.fixture
+def sample_department(db, sample_business_unit):
+    """建立測試用部門"""
+    from app.models.department import Department
+    dept = Department(
+        tenant_id=1,
+        business_unit_id=sample_business_unit.id,
+        name="資訊部",
+        code="IT",
+        is_active=True,
+    )
+    db.add(dept)
+    db.commit()
+    db.refresh(dept)
+    return dept
+
+
+@pytest.fixture
+def sample_employee(db, sample_business_unit):
+    """建立測試用員工"""
+    from app.models.employee import Employee
+    import datetime
+    emp = Employee(
+        tenant_id=1,
+        employee_id="EMP001",
+        username_base="test.user",
+        legal_name="測試用戶",
+        english_name="Test User",
+        hire_date=datetime.date.today(),
+        status="active",
+    )
+    db.add(emp)
+    db.commit()
+    db.refresh(emp)
+    return emp