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/__init__.py

@@ -0,0 +1,107 @@
+"""
+Schemas 模組
+匯出所有 Pydantic Schemas
+"""
+
+# Base
+from app.schemas.base import (
+    BaseSchema,
+    TimestampSchema,
+    PaginationParams,
+    PaginatedResponse,
+)
+
+# Employee
+from app.schemas.employee import (
+    EmployeeBase,
+    EmployeeCreate,
+    EmployeeUpdate,
+    EmployeeInDB,
+    EmployeeResponse,
+    EmployeeListItem,
+    EmployeeDetail,
+)
+
+# Business Unit
+from app.schemas.business_unit import (
+    BusinessUnitBase,
+    BusinessUnitCreate,
+    BusinessUnitUpdate,
+    BusinessUnitInDB,
+    BusinessUnitResponse,
+    BusinessUnitListItem,
+)
+
+# Department
+from app.schemas.department import (
+    DepartmentBase,
+    DepartmentCreate,
+    DepartmentUpdate,
+    DepartmentResponse,
+    DepartmentListItem,
+    DepartmentTreeNode,
+)
+
+# Employee Identity
+from app.schemas.employee_identity import (
+    EmployeeIdentityBase,
+    EmployeeIdentityCreate,
+    EmployeeIdentityUpdate,
+    EmployeeIdentityInDB,
+    EmployeeIdentityResponse,
+    EmployeeIdentityListItem,
+)
+
+# Network Drive
+from app.schemas.network_drive import (
+    NetworkDriveBase,
+    NetworkDriveCreate,
+    NetworkDriveUpdate,
+    NetworkDriveInDB,
+    NetworkDriveResponse,
+    NetworkDriveListItem,
+    NetworkDriveQuotaUpdate,
+)
+
+# Audit Log
+from app.schemas.audit_log import (
+    AuditLogBase,
+    AuditLogCreate,
+    AuditLogInDB,
+    AuditLogResponse,
+    AuditLogListItem,
+    AuditLogFilter,
+)
+
+# Email Account
+from app.schemas.email_account import (
+    EmailAccountBase,
+    EmailAccountCreate,
+    EmailAccountUpdate,
+    EmailAccountInDB,
+    EmailAccountResponse,
+    EmailAccountListItem,
+    EmailAccountQuotaUpdate,
+)
+
+# Permission
+from app.schemas.permission import (
+    PermissionBase,
+    PermissionCreate,
+    PermissionUpdate,
+    PermissionInDB,
+    PermissionResponse,
+    PermissionListItem,
+    PermissionBatchCreate,
+    PermissionFilter,
+    VALID_SYSTEMS,
+    VALID_ACCESS_LEVELS,
+)
+
+# Response
+from app.schemas.response import (
+    ResponseModel,
+    ErrorResponse,
+    MessageResponse,
+    SuccessResponse,
+)