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/response.py

@@ -0,0 +1,37 @@
+"""
+通用響應 Schemas
+"""
+from typing import Optional, Any, Generic, TypeVar
+from pydantic import BaseModel, Field
+
+T = TypeVar('T')
+
+
+class ResponseModel(BaseModel, Generic[T]):
+    """通用響應模型"""
+
+    success: bool = Field(True, description="操作是否成功")
+    message: Optional[str] = Field(None, description="響應訊息")
+    data: Optional[T] = Field(None, description="響應數據")
+
+
+class ErrorResponse(BaseModel):
+    """錯誤響應"""
+
+    success: bool = Field(False, description="操作是否成功")
+    message: str = Field(..., description="錯誤訊息")
+    error_code: Optional[str] = Field(None, description="錯誤代碼")
+    details: Optional[Any] = Field(None, description="錯誤詳情")
+
+
+class MessageResponse(BaseModel):
+    """簡單訊息響應"""
+
+    message: str = Field(..., description="響應訊息")
+
+
+class SuccessResponse(BaseModel):
+    """成功響應"""
+
+    success: bool = Field(True, description="操作是否成功")
+    message: str = Field(..., description="成功訊息")