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/app/schemas/business_unit.py

@@ -0,0 +1,89 @@
+"""
+事業部 Schemas
+"""
+from datetime import datetime
+from typing import Optional
+from pydantic import Field, ConfigDict
+
+from app.schemas.base import BaseSchema
+
+
+class BusinessUnitBase(BaseSchema):
+    """事業部基礎 Schema"""
+
+    name: str = Field(..., min_length=2, max_length=100, description="事業部名稱")
+    name_en: Optional[str] = Field(None, max_length=100, description="英文名稱")
+    code: str = Field(..., min_length=2, max_length=20, description="事業部代碼")
+    email_domain: str = Field(..., description="郵件網域")
+    description: Optional[str] = Field(None, description="說明")
+
+
+class BusinessUnitCreate(BusinessUnitBase):
+    """創建事業部 Schema"""
+
+    model_config = ConfigDict(
+        json_schema_extra={
+            "example": {
+                "name": "業務發展部",
+                "name_en": "Business Development",
+                "code": "biz",
+                "email_domain": "ease.taipei",
+                "description": "碳權申請諮詢、碳足跡盤查、碳權交易媒合、業務拓展"
+            }
+        }
+    )
+
+
+class BusinessUnitUpdate(BaseSchema):
+    """更新事業部 Schema"""
+
+    name: Optional[str] = Field(None, min_length=2, max_length=100)
+    name_en: Optional[str] = Field(None, max_length=100)
+    description: Optional[str] = None
+    is_active: Optional[bool] = None
+
+
+class BusinessUnitInDB(BusinessUnitBase):
+    """資料庫中的事業部 Schema"""
+
+    id: int
+    is_active: bool
+    created_at: datetime
+
+    model_config = ConfigDict(from_attributes=True)
+
+
+class BusinessUnitResponse(BusinessUnitInDB):
+    """事業部響應 Schema"""
+
+    departments_count: Optional[int] = Field(None, description="部門數量")
+    employees_count: Optional[int] = Field(None, description="員工數量")
+
+    model_config = ConfigDict(
+        json_schema_extra={
+            "example": {
+                "id": 1,
+                "name": "業務發展部",
+                "name_en": "Business Development",
+                "code": "biz",
+                "email_domain": "ease.taipei",
+                "description": "碳權申請諮詢、碳足跡盤查、碳權交易媒合、業務拓展",
+                "is_active": True,
+                "created_at": "2020-01-01T00:00:00",
+                "departments_count": 3,
+                "employees_count": 15
+            }
+        }
+    )
+
+
+class BusinessUnitListItem(BaseSchema):
+    """事業部列表項 Schema"""
+
+    id: int
+    name: str
+    code: str
+    email_domain: str
+    is_active: bool
+
+    model_config = ConfigDict(from_attributes=True)