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/README_ADD_COMPANY_INFO.md

@@ -0,0 +1,49 @@
+# 修正「公司資料維護」功能代碼 (ID=17)
+
+## 現況說明
+
+資料庫中已存在 ID=17 的「公司資料維護」記錄,僅需修正 code 和 module_code 以符合前端路徑。
+
+### 修正項目:
+- `code`: `tenant` → `company-info`
+- `module_code`: `tenant` → `company-info`
+- `module_functions`: `["Read", "Update"]` → `["View", "Update"]` (統一用詞)
+
+其他設定 (`upper_function_id=0`, `is_mana=false`) 都是正確的。
+
+## 執行步驟
+
+連線到資料庫後執行 `update_func_17.sql`:
+
+```sql
+UPDATE system_functions
+SET
+    code = 'company-info',
+    module_code = 'company-info',
+    module_functions = '["View", "Update"]'::jsonb
+WHERE id = 17;
+```
+
+## 確認修正
+
+```sql
+SELECT id, code, module_code, name, module_functions
+FROM system_functions
+WHERE id = 17;
+```
+
+應該顯示:
+```
+id | code         | module_code  | name         | module_functions
+---+--------------+--------------+--------------+------------------
+17 | company-info | company-info | 公司資料維護 | ["View","Update"]
+```
+
+## 功能說明
+
+- **前端路徑**: `/company-info`
+- **後端 API**:
+  - GET `/api/v1/tenants/current` - 取得當前租戶資料
+  - PATCH `/api/v1/tenants/current` - 更新當前租戶資料
+- **功能定位**: 人資資料維護功能 (is_mana = false)
+- **權限**: View, Update