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/department.py

@@ -0,0 +1,125 @@
+"""
+部門 Schemas (統一樹狀結構)
+"""
+from datetime import datetime
+from typing import Optional, List, Any
+from pydantic import Field, ConfigDict
+
+from app.schemas.base import BaseSchema
+
+
+class DepartmentBase(BaseSchema):
+    """部門基礎 Schema"""
+
+    name: str = Field(..., min_length=2, max_length=100, description="部門名稱")
+    name_en: Optional[str] = Field(None, max_length=100, description="英文名稱")
+    code: str = Field(..., min_length=1, max_length=20, description="部門代碼")
+    description: Optional[str] = Field(None, description="說明")
+
+
+class DepartmentCreate(DepartmentBase):
+    """創建部門 Schema
+
+    - parent_id=NULL: 建立第一層部門，可設定 email_domain
+    - parent_id=有值: 建立子部門，不可設定 email_domain (繼承)
+    """
+
+    parent_id: Optional[int] = Field(None, description="上層部門 ID (NULL=第一層)")
+    email_domain: Optional[str] = Field(None, max_length=100,
+                                         description="郵件網域 (只有第一層可設定，例如 ease.taipei)")
+    email_address: Optional[str] = Field(None, max_length=255, description="部門信箱")
+    email_quota_mb: Optional[int] = Field(5120, description="部門信箱配額 (MB)")
+
+    model_config = ConfigDict(
+        json_schema_extra={
+            "example": {
+                "parent_id": None,
+                "name": "業務發展部",
+                "name_en": "Business Development",
+                "code": "BD",
+                "email_domain": "ease.taipei",
+                "description": "業務發展相關部門"
+            }
+        }
+    )
+
+
+class DepartmentUpdate(BaseSchema):
+    """更新部門 Schema
+
+    注意: code 和 parent_id 建立後不可修改
+    email_domain 只有第一層 (depth=0) 可更新
+    """
+
+    name: Optional[str] = Field(None, min_length=2, max_length=100)
+    name_en: Optional[str] = Field(None, max_length=100)
+    description: Optional[str] = None
+    email_domain: Optional[str] = Field(None, max_length=100,
+                                         description="只有第一層部門可更新")
+    email_address: Optional[str] = Field(None, max_length=255)
+    email_quota_mb: Optional[int] = None
+    is_active: Optional[bool] = None
+
+
+class DepartmentResponse(BaseSchema):
+    """部門響應 Schema"""
+
+    id: int
+    tenant_id: int
+    parent_id: Optional[int] = None
+    code: str
+    name: str
+    name_en: Optional[str] = None
+    depth: int
+    email_domain: Optional[str] = None
+    effective_email_domain: Optional[str] = None
+    email_address: Optional[str] = None
+    email_quota_mb: int
+    description: Optional[str] = None
+    is_active: bool
+    is_top_level: bool = False
+    created_at: datetime
+    parent_name: Optional[str] = None
+    member_count: Optional[int] = None
+
+    model_config = ConfigDict(from_attributes=True)
+
+
+class DepartmentListItem(BaseSchema):
+    """部門列表項 Schema"""
+
+    id: int
+    tenant_id: int
+    parent_id: Optional[int] = None
+    code: str
+    name: str
+    depth: int
+    email_domain: Optional[str] = None
+    effective_email_domain: Optional[str] = None
+    email_address: Optional[str] = None
+    is_active: bool
+    member_count: Optional[int] = None
+
+    model_config = ConfigDict(from_attributes=True)
+
+
+class DepartmentTreeNode(BaseSchema):
+    """部門樹狀節點 Schema (遞迴)"""
+
+    id: int
+    code: str
+    name: str
+    name_en: Optional[str] = None
+    depth: int
+    parent_id: Optional[int] = None
+    email_domain: Optional[str] = None
+    effective_email_domain: Optional[str] = None
+    email_address: Optional[str] = None
+    email_quota_mb: int
+    description: Optional[str] = None
+    is_active: bool
+    is_top_level: bool
+    member_count: int = 0
+    children: List[Any] = []
+
+    model_config = ConfigDict(from_attributes=True)