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>

frontend/services/email-accounts.ts

@@ -0,0 +1,73 @@
+/**
+ * 郵件帳號服務
+ * 處理所有與郵件帳號相關的 API 請求
+ */
+import { apiClient } from '@/lib/api-client'
+import type {
+  EmailAccount,
+  CreateEmailAccountInput,
+  UpdateEmailAccountInput,
+  EmailAccountQuotaUpdate,
+  PaginatedResponse,
+} from '@/types'
+
+export interface EmailAccountListParams {
+  page?: number
+  page_size?: number
+  employee_id?: number
+  is_active?: boolean
+  search?: string
+}
+
+export const emailAccountsService = {
+  /**
+   * 獲取郵件帳號列表
+   */
+  async list(params?: EmailAccountListParams): Promise<PaginatedResponse<EmailAccount>> {
+    return apiClient.get<PaginatedResponse<EmailAccount>>('/email-accounts', {
+      params,
+    })
+  },
+
+  /**
+   * 獲取郵件帳號詳情
+   */
+  async get(id: number): Promise<EmailAccount> {
+    return apiClient.get<EmailAccount>(`/email-accounts/${id}`)
+  },
+
+  /**
+   * 創建郵件帳號
+   */
+  async create(data: CreateEmailAccountInput): Promise<EmailAccount> {
+    return apiClient.post<EmailAccount>('/email-accounts', data)
+  },
+
+  /**
+   * 更新郵件帳號
+   */
+  async update(id: number, data: UpdateEmailAccountInput): Promise<EmailAccount> {
+    return apiClient.put<EmailAccount>(`/email-accounts/${id}`, data)
+  },
+
+  /**
+   * 更新郵件配額
+   */
+  async updateQuota(id: number, data: EmailAccountQuotaUpdate): Promise<EmailAccount> {
+    return apiClient.patch<EmailAccount>(`/email-accounts/${id}/quota`, data)
+  },
+
+  /**
+   * 停用郵件帳號 (軟刪除)
+   */
+  async delete(id: number): Promise<{ message: string }> {
+    return apiClient.delete<{ message: string }>(`/email-accounts/${id}`)
+  },
+
+  /**
+   * 獲取員工的所有郵件帳號
+   */
+  async getByEmployee(employeeId: number): Promise<EmailAccount[]> {
+    return apiClient.get<EmailAccount[]>(`/email-accounts/employees/${employeeId}/email-accounts`)
+  },
+}