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/tests/test_site_contact_display.py

@@ -0,0 +1,40 @@
+import uuid
+
+import pytest
+
+from app.models.user import User
+from app.services.site_contact_display import build_contact_display
+
+
+def make_user(user_id: uuid.UUID, full_name: str, email: str) -> User:
+    return User(
+        id=user_id,
+        email=email,
+        password_hash="hash",
+        full_name=full_name,
+        clinical_department="PMO",
+    )
+
+
+def test_build_contact_display_resolves_comma_separated_user_ids():
+    first_id = uuid.uuid4()
+    second_id = uuid.uuid4()
+    users = {
+        first_id: make_user(first_id, "张三", "zhangsan@example.com"),
+        second_id: make_user(second_id, "李四", "lisi@example.com"),
+    }
+
+    display = build_contact_display(f"{first_id}, {second_id}", users)
+
+    assert display == "张三、李四"
+
+
+@pytest.mark.parametrize("role", ["PM", "CRA", "PV", "QA", "CTA"])
+def test_build_contact_display_is_role_independent_for_site_read_roles(role: str):
+    user_id = uuid.uuid4()
+    users = {user_id: make_user(user_id, "周成", "zhoucheng@example.com")}
+
+    display = build_contact_display(str(user_id), users)
+
+    assert role
+    assert display == "周成"