权限管理：新增医学审核项目角色

新增 MEDICAL_REVIEW 项目角色，界面显示为医学审核，并通过 Alembic 迁移扩展 user_role 枚举。

为医学审核配置独立默认权限：项目总览、参与者、风险问题、监查稽查、FAQ、共享库按医学审核职责开放，不再复制 PV 默认权限。

同步前后端类型、项目成员角色下拉、权限矩阵展示、文件分发角色兜底和用户协议文案，并补充权限矩阵回归测试。

backend/app/schemas/member.py

@@ -5,7 +5,7 @@ from typing import Literal, Optional
 from pydantic import BaseModel, ConfigDict, Field
 from app.schemas.user import UserDisplay
 
-StudyRole = Literal["PM", "CRA", "PV", "IMP", "QA", "ADMIN"]
+StudyRole = Literal["PM", "CRA", "PV", "MEDICAL_REVIEW", "IMP", "QA", "ADMIN"]
 
 
 class StudyMemberCreate(BaseModel):

backend/app/schemas/project_permission.py

@@ -5,7 +5,7 @@ from typing import Literal
 from pydantic import BaseModel, Field
 
 
-ProjectPermissionRole = Literal["ADMIN", "PM", "CRA", "PV", "IMP", "QA"]
+ProjectPermissionRole = Literal["ADMIN", "PM", "CRA", "PV", "MEDICAL_REVIEW", "IMP", "QA"]
 ProjectPermissionAction = Literal["read", "write"]
 
 

backend/app/schemas/user.py

@@ -5,8 +5,8 @@ from typing import Literal, Optional
 
 from pydantic import BaseModel, ConfigDict, EmailStr, Field, field_validator
 
-UserRole = Literal["PM", "CRA", "PV", "IMP", "QA", "ADMIN"]
-RegisterRole = Literal["PM", "CRA", "PV", "IMP"]
+UserRole = Literal["PM", "CRA", "PV", "MEDICAL_REVIEW", "IMP", "QA", "ADMIN"]
+RegisterRole = Literal["PM", "CRA", "PV", "MEDICAL_REVIEW", "IMP"]
 UserStatus = Literal["PENDING", "ACTIVE", "REJECTED", "DISABLED"]
 
 PASSWORD_REGEX = re.compile(r"^(?=.*[A-Za-z])(?=.*\d).{8,}$")