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/scripts/add_company_info_function.sql

@@ -0,0 +1,36 @@
+-- 新增「公司資料維護」系統功能
+-- 日期: 2026-02-23
+-- 說明: 允許使用者查看和編輯當前租戶的公司基本資料
+
+INSERT INTO system_functions (
+    code,
+    name,
+    function_type,
+    upper_function_id,
+    "order",
+    function_icon,
+    module_code,
+    module_functions,
+    description,
+    is_mana,
+    is_active,
+    edit_by
+) VALUES (
+    'company-info',
+    '公司資料維護',
+    2,  -- FUNCTION (非 NODE)
+    1,  -- 假設掛在「系統管理」(id=1) 節點下
+    15,
+    '🏢',
+    'company-info',
+    '["View", "Update"]'::jsonb,
+    '管理當前租戶的公司基本資料，包含公司名稱、統一編號、聯絡資訊等',
+    true,  -- 系統管理功能
+    true,  -- 啟用
+    1      -- edit_by
+);
+
+-- 確認新增結果
+SELECT id, code, name, function_type, upper_function_id, "order"
+FROM system_functions
+WHERE code = 'company-info';