ADD file via upload

DesignDiagrams

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+设计图示（类图与时序图）
+
+1. 类关系图（简化）
+```mermaid
+classDiagram
+  class DeptController
+  class EmployeeController
+  class EmployeeKpiController
+  class HireNumController
+  class SalaryLevelController
+  class LoginController
+  class CaptchaController
+
+  class IDeptService
+  class IEmployeeService
+  class IEmployeeKpiService
+  class IHireNumService
+  class ISalaryLevelService
+
+  class Dept
+  class Employee
+  class EmployeeKpi
+  class HireNum
+  class SalaryLevel
+
+  DeptController --> IDeptService
+  EmployeeController --> IEmployeeService
+  EmployeeKpiController --> IEmployeeKpiService
+  HireNumController --> IHireNumService
+  SalaryLevelController --> ISalaryLevelService
+
+  IDeptService --> Dept
+  IEmployeeService --> Employee
+  IEmployeeKpiService --> EmployeeKpi
+  IHireNumService --> HireNum
+  ISalaryLevelService --> SalaryLevel
+```
+
+2. 登录时序图
+```mermaid
+sequenceDiagram
+  participant U as User
+  participant FE as Frontend(Vue)
+  participant BE as Backend(Spring Boot)
+  participant REDIS as Redis
+
+  U->>FE: 打开登录页
+  FE->>BE: GET /captchaImage
+  BE->>REDIS: 保存(uuid -> code)
+  BE-->>FE: uuid, img(Base64)
+  U->>FE: 输入 username/password/code
+  FE->>BE: POST /login {username,password,code,uuid}
+  BE->>REDIS: 校验 code
+  BE-->>FE: token
+  FE->>FE: 保存 Admin-Token(Cookie)
+```
+
+3. 分页查询时序图
+```mermaid
+sequenceDiagram
+  participant FE as Frontend
+  participant CTRL as Controller
+  participant SVC as Service
+  participant DAO as Mapper/Repo
+
+  FE->>CTRL: GET /<module>/list?query
+  CTRL->>CTRL: startPage()
+  CTRL->>SVC: select*List(query)
+  SVC->>DAO: 查询
+  DAO-->>SVC: 列表数据
+  SVC-->>CTRL: 列表数据
+  CTRL-->>FE: TableDataInfo
+```
+
+