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>

frontend/app/departments/layout.tsx

@@ -0,0 +1,53 @@
+/**
+ * Departments 佈局
+ */
+'use client'
+
+import { useSession } from 'next-auth/react'
+import { useRouter } from 'next/navigation'
+import { useEffect } from 'react'
+import { Sidebar } from '@/components/layout/sidebar'
+import { Breadcrumb } from '@/components/layout/breadcrumb'
+
+export default function DepartmentsLayout({ children }: { children: React.ReactNode }) {
+  const { data: session, status } = useSession()
+  const router = useRouter()
+
+  useEffect(() => {
+    if (status === 'unauthenticated') {
+      router.push('/auth/signin')
+    }
+  }, [status, router])
+
+  if (status === 'loading') {
+    return (
+      <div className="min-h-screen flex items-center justify-center">
+        <div className="text-center">
+          <div className="w-16 h-16 border-4 border-indigo-600 border-t-transparent rounded-full animate-spin mx-auto mb-4"></div>
+          <p className="text-gray-600">載入中...</p>
+        </div>
+      </div>
+    )
+  }
+
+  if (!session) {
+    return null
+  }
+
+  return (
+    <div className="flex h-screen bg-gray-100">
+      {/* Sidebar */}
+      <aside className="w-64 flex-shrink-0">
+        <Sidebar />
+      </aside>
+
+      {/* Main Content */}
+      <main className="flex-1 overflow-auto">
+        <div className="p-8">
+          <Breadcrumb />
+          {children}
+        </div>
+      </main>
+    </div>
+  )
+}