feat(subject): 参与者状态依赖筛选日期并支持后续编辑

- 未填写筛选日期的参与者不再默认进入 SCREENING，状态显示为占位符。
- SubjectUpdate 不再开放 status 入参，改由后端依据日期推导，并新增
  screening_date 字段允许 PM/CRA 后续补录筛选日期。
- 参与者管理页与详情页同步：详情页支持编辑筛选日期，列表页与详情页
  在没有筛选日期时显示占位符而非旧 enum 值。

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/app/crud/subject.py

@@ -34,6 +34,9 @@ def _standard_visit_codes(visit_schedule: list[dict] | None) -> set[str]:
 
 
 def derive_subject_status(subject, visits: Sequence[Visit], visit_schedule: list[dict] | None = None) -> str:
+    if not getattr(subject, "screening_date", None):
+        return ""
+
     if any(_visit_code(visit) == "提前终止" and getattr(visit, "actual_date", None) for visit in visits):
         return "DROPPED"
 
@@ -116,7 +119,7 @@ async def create_subject(db: AsyncSession, study_id: uuid.UUID, subject_in: Subj
         study_id=study_id,
         site_id=subject_in.site_id,
         subject_no=subject_in.subject_no,
-        status="SCREENING",
+        status="SCREENING" if subject_in.screening_date else "",
         screening_date=subject_in.screening_date,
         consent_date=subject_in.consent_date,
         enrollment_date=subject_in.enrollment_date,
@@ -194,8 +197,7 @@ async def generate_default_visits(db: AsyncSession, subject: Subject) -> None:
 
 async def update_subject(db: AsyncSession, subject: Subject, subject_in: SubjectUpdate) -> Subject:
     update_data = subject_in.model_dump(exclude_unset=True)
-    update_data.pop("status", None)
-    next_screening_date = subject.screening_date
+    next_screening_date = update_data.get("screening_date", subject.screening_date)
     next_consent_date = update_data.get("consent_date", subject.consent_date)
     next_enrollment_date = update_data.get("enrollment_date", subject.enrollment_date)
     next_completion_date = update_data.get("completion_date", subject.completion_date)

backend/app/schemas/subject.py

@@ -15,7 +15,7 @@ class SubjectCreate(BaseModel):
 
 
 class SubjectUpdate(BaseModel):
-    status: Optional[str] = None
+    screening_date: Optional[date] = None
     consent_date: Optional[date] = None
     enrollment_date: Optional[date] = None
     baseline_date: Optional[date] = None

backend/tests/test_subject_medication_adherence.py

@@ -1,4 +1,4 @@
-from datetime import datetime
+from datetime import date, datetime
 from types import SimpleNamespace
 import uuid
 
@@ -12,6 +12,16 @@ def test_subject_update_accepts_actual_medication_count():
     assert payload.actual_medication_count == 12
 
 
+def test_subject_update_accepts_screening_date():
+    payload = SubjectUpdate(screening_date=date(2026, 5, 25))
+
+    assert payload.screening_date == date(2026, 5, 25)
+
+
+def test_subject_update_does_not_expose_status_input():
+    assert "status" not in SubjectUpdate.model_fields
+
+
 def test_subject_read_includes_actual_medication_count():
     subject = SimpleNamespace(
         id=uuid.UUID("00000000-0000-0000-0000-000000000001"),

backend/tests/test_visit_schedule.py

@@ -275,3 +275,9 @@ def test_derive_subject_status_marks_screening_until_enrollment_date_is_filled()
     subject = SimpleNamespace(screening_date=date(2026, 5, 1), enrollment_date=None)
 
     assert derive_subject_status(subject, [], []) == "SCREENING"
+
+
+def test_derive_subject_status_is_empty_before_screening_date_is_filled():
+    subject = SimpleNamespace(screening_date=None, enrollment_date=None)
+
+    assert derive_subject_status(subject, [], []) == ""