优化中心联系人展示名称解析

- 新增中心联系人展示名解析服务，支持从逗号分隔用户 ID 解析姓名\n- 中心列表接口返回 contact_display，避免前端依赖项目成员权限才能展示联系人姓名\n- 中心管理和立项会议授权页面优先使用后端联系人展示名\n- 补充联系人解析服务测试和立项会议授权页面展示顺序测试

backend/app/api/v1/sites.py

@@ -10,8 +10,10 @@ from app.crud import audit as audit_crud
 from app.crud import site as site_crud
 from app.crud import startup as startup_crud
 from app.crud import study as study_crud
+from app.crud import user as user_crud
 from app.schemas.site import SiteCreate, SiteRead, SiteUpdate
 from app.schemas.startup import StartupEthicsCreate, StartupFeasibilityCreate
+from app.services.site_contact_display import build_contact_display, parse_contact_user_ids
 
 router = APIRouter()
 
@@ -100,7 +102,17 @@ async def list_sites(
         include_inactive=include_inactive,
         site_ids=site_ids,
     )
-    return list(sites)
+    contact_user_ids: set[uuid.UUID] = set()
+    for site in sites:
+        contact_user_ids.update(parse_contact_user_ids(site.contact))
+    users_map = await user_crud.get_users_by_ids(db, contact_user_ids)
+
+    result: list[SiteRead] = []
+    for site in sites:
+        item = SiteRead.model_validate(site)
+        item.contact_display = build_contact_display(site.contact, users_map)
+        result.append(item)
+    return result
 
 
 @router.patch(