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/system_function.py

@@ -0,0 +1,114 @@
+"""
+SystemFunction Schemas
+系統功能明細 API 資料結構
+"""
+from typing import List, Optional
+from pydantic import BaseModel, Field, field_validator
+from datetime import datetime
+
+
+class SystemFunctionBase(BaseModel):
+    """系統功能基礎 Schema"""
+    code: str = Field(..., max_length=200, description="系統功能代碼/功能英文名稱")
+    upper_function_id: int = Field(0, description="上層功能代碼 (0為初始層)")
+    name: str = Field(..., max_length=200, description="系統功能中文名稱")
+    function_type: int = Field(..., description="系統功能類型 (1:node, 2:function)")
+    order: int = Field(..., description="系統功能次序")
+    function_icon: str = Field("", max_length=200, description="功能圖示")
+    module_code: Optional[str] = Field(None, max_length=200, description="功能模組名稱")
+    module_functions: List[str] = Field(default_factory=list, description="模組項目")
+    description: str = Field("", description="說明 (富文本格式)")
+    is_mana: bool = Field(True, description="系統管理")
+    is_active: bool = Field(True, description="啟用")
+
+    @field_validator('function_type')
+    @classmethod
+    def validate_function_type(cls, v):
+        """驗證功能類型"""
+        if v not in [1, 2]:
+            raise ValueError('function_type 必須為 1 (node) 或 2 (function)')
+        return v
+
+    @field_validator('module_functions')
+    @classmethod
+    def validate_module_functions(cls, v):
+        """驗證模組項目"""
+        allowed_functions = ['View', 'Create', 'Read', 'Update', 'Delete', 'Print', 'File']
+        for func in v:
+            if func not in allowed_functions:
+                raise ValueError(f'module_functions 只能包含: {", ".join(allowed_functions)}')
+        return v
+
+    @field_validator('upper_function_id')
+    @classmethod
+    def validate_upper_function_id(cls, v, values):
+        """驗證上層功能代碼"""
+        # upper_function_id 必須是 function_type=1 且 is_active=1 的功能, 或 0 (初始層)
+        if v < 0:
+            raise ValueError('upper_function_id 不能小於 0')
+        return v
+
+
+class SystemFunctionCreate(SystemFunctionBase):
+    """系統功能建立 Schema"""
+    edit_by: int = Field(..., description="資料建立者")
+
+    @field_validator('module_code')
+    @classmethod
+    def validate_module_code_create(cls, v, info):
+        """驗證 module_code (function_type=2 必填)"""
+        function_type = info.data.get('function_type')
+        if function_type == 2 and not v:
+            raise ValueError('function_type=2 時, module_code 為必填')
+        if function_type == 1 and v:
+            raise ValueError('function_type=1 時, module_code 不能輸入')
+        return v
+
+    @field_validator('module_functions')
+    @classmethod
+    def validate_module_functions_create(cls, v, info):
+        """驗證 module_functions (function_type=2 必填)"""
+        function_type = info.data.get('function_type')
+        if function_type == 2 and not v:
+            raise ValueError('function_type=2 時, module_functions 為必填')
+        return v
+
+
+class SystemFunctionUpdate(BaseModel):
+    """系統功能更新 Schema (部分更新)"""
+    code: Optional[str] = Field(None, max_length=200)
+    upper_function_id: Optional[int] = None
+    name: Optional[str] = Field(None, max_length=200)
+    function_type: Optional[int] = None
+    order: Optional[int] = None
+    function_icon: Optional[str] = Field(None, max_length=200)
+    module_code: Optional[str] = Field(None, max_length=200)
+    module_functions: Optional[List[str]] = None
+    description: Optional[str] = None
+    is_mana: Optional[bool] = None
+    is_active: Optional[bool] = None
+    edit_by: int = Field(..., description="資料編輯者")
+
+
+class SystemFunctionInDB(SystemFunctionBase):
+    """系統功能資料庫 Schema"""
+    id: int
+    edit_by: int
+    created_at: datetime
+    updated_at: Optional[datetime] = None
+
+    class Config:
+        from_attributes = True
+
+
+class SystemFunctionResponse(SystemFunctionInDB):
+    """系統功能回應 Schema"""
+    pass
+
+
+class SystemFunctionListResponse(BaseModel):
+    """系統功能列表回應"""
+    total: int
+    items: List[SystemFunctionResponse]
+    page: int
+    page_size: int