中文：收口权限与中心/立项配置改造

backend/app/core/deps.py

@@ -95,7 +95,7 @@ def require_study_member():
     return dependency
 
 
-def require_study_roles(roles: Iterable[str]):
+def require_study_roles(roles: Iterable[str], *, allow_system_admin: bool = True):
     roles_set = set(roles)
 
     async def dependency(
@@ -104,7 +104,7 @@ def require_study_roles(roles: Iterable[str]):
         db: AsyncSession = Depends(get_db_session),
     ):
         role_value = current_user.role.value if hasattr(current_user.role, "value") else current_user.role
-        if role_value == "ADMIN":
+        if allow_system_admin and role_value == "ADMIN":
             return current_user
         membership = await member_crud.get_member(db, study_id, current_user.id)
         if not membership or not membership.is_active or membership.role_in_study not in roles_set: