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/test-session/page.tsx

@@ -0,0 +1,45 @@
+'use client'
+
+import { useSession } from 'next-auth/react'
+
+export default function TestSessionPage() {
+  const { data: session, status } = useSession()
+
+  return (
+    <div style={{ padding: '20px', fontFamily: 'monospace' }}>
+      <h1>Session Debug Page</h1>
+
+      <div style={{ marginTop: '20px' }}>
+        <h2>Status: {status}</h2>
+      </div>
+
+      <div style={{ marginTop: '20px' }}>
+        <h2>Session Data:</h2>
+        <pre style={{ background: '#f5f5f5', padding: '10px', borderRadius: '5px' }}>
+          {JSON.stringify(session, null, 2)}
+        </pre>
+      </div>
+
+      <div style={{ marginTop: '20px' }}>
+        <h2>Session User:</h2>
+        <pre style={{ background: '#f5f5f5', padding: '10px', borderRadius: '5px' }}>
+          {JSON.stringify(session?.user, null, 2)}
+        </pre>
+      </div>
+
+      <div style={{ marginTop: '20px' }}>
+        <h2>Tenant Info:</h2>
+        <pre style={{ background: '#f5f5f5', padding: '10px', borderRadius: '5px' }}>
+          {JSON.stringify((session?.user as any)?.tenant, null, 2)}
+        </pre>
+      </div>
+
+      <div style={{ marginTop: '20px' }}>
+        <h2>is_sysmana:</h2>
+        <pre style={{ background: '#f5f5f5', padding: '10px', borderRadius: '5px', fontSize: '24px', fontWeight: 'bold' }}>
+          {(session?.user as any)?.tenant?.is_sysmana?.toString() || 'undefined'}
+        </pre>
+      </div>
+    </div>
+  )
+}