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/email_account.py

@@ -0,0 +1,126 @@
+"""
+郵件帳號 Schemas
+"""
+from datetime import datetime
+from typing import Optional
+from pydantic import BaseModel, Field, EmailStr, ConfigDict, field_validator
+
+from app.schemas.base import BaseSchema, TimestampSchema
+
+
+class EmailAccountBase(BaseSchema):
+    """郵件帳號基礎 Schema"""
+
+    email_address: EmailStr = Field(..., description="郵件地址")
+    quota_mb: int = Field(2048, ge=1024, le=102400, description="配額 (MB), 1GB-100GB")
+    forward_to: Optional[EmailStr] = Field(None, description="轉寄地址")
+    auto_reply: Optional[str] = Field(None, max_length=1000, description="自動回覆內容")
+    is_active: bool = Field(True, description="是否啟用")
+
+
+class EmailAccountCreate(EmailAccountBase):
+    """創建郵件帳號 Schema"""
+
+    employee_id: int = Field(..., description="員工 ID")
+
+    model_config = ConfigDict(
+        json_schema_extra={
+            "example": {
+                "employee_id": 1,
+                "email_address": "porsche.chen@porscheworld.tw",
+                "quota_mb": 2048,
+                "forward_to": None,
+                "auto_reply": None,
+                "is_active": True
+            }
+        }
+    )
+
+
+class EmailAccountUpdate(BaseSchema):
+    """更新郵件帳號 Schema"""
+
+    quota_mb: Optional[int] = Field(None, ge=1024, le=102400, description="配額 (MB)")
+    forward_to: Optional[EmailStr] = Field(None, description="轉寄地址")
+    auto_reply: Optional[str] = Field(None, max_length=1000, description="自動回覆內容")
+    is_active: Optional[bool] = Field(None, description="是否啟用")
+
+    @field_validator('forward_to')
+    @classmethod
+    def validate_forward_to(cls, v):
+        """允許空字串來清除轉寄地址"""
+        if v == "":
+            return None
+        return v
+
+    @field_validator('auto_reply')
+    @classmethod
+    def validate_auto_reply(cls, v):
+        """允許空字串來清除自動回覆"""
+        if v == "":
+            return None
+        return v
+
+
+class EmailAccountInDB(EmailAccountBase, TimestampSchema):
+    """資料庫中的郵件帳號 Schema"""
+
+    id: int
+    tenant_id: int
+    employee_id: int
+
+    model_config = ConfigDict(from_attributes=True)
+
+
+class EmailAccountResponse(EmailAccountInDB):
+    """郵件帳號響應 Schema (包含關聯資料)"""
+
+    employee_name: Optional[str] = Field(None, description="員工姓名")
+    employee_number: Optional[str] = Field(None, description="員工編號")
+
+    model_config = ConfigDict(
+        json_schema_extra={
+            "example": {
+                "id": 1,
+                "tenant_id": 1,
+                "employee_id": 1,
+                "email_address": "porsche.chen@porscheworld.tw",
+                "quota_mb": 2048,
+                "forward_to": None,
+                "auto_reply": None,
+                "is_active": True,
+                "employee_name": "陳保時",
+                "employee_number": "EMP001",
+                "created_at": "2020-01-01T00:00:00",
+                "updated_at": "2020-01-01T00:00:00"
+            }
+        }
+    )
+
+
+class EmailAccountListItem(BaseSchema):
+    """郵件帳號列表項 Schema (簡化版)"""
+
+    id: int
+    email_address: str
+    quota_mb: int
+    is_active: bool
+    employee_id: int
+    employee_name: Optional[str] = None
+    employee_number: Optional[str] = None
+
+    model_config = ConfigDict(from_attributes=True)
+
+
+class EmailAccountQuotaUpdate(BaseSchema):
+    """郵件配額更新 Schema"""
+
+    quota_mb: int = Field(..., ge=1024, le=102400, description="配額 (MB), 1GB-100GB")
+
+    model_config = ConfigDict(
+        json_schema_extra={
+            "example": {
+                "quota_mb": 5120  # 5GB
+            }
+        }
+    )