功能(提醒)：统一项目提醒中心与桌面通知链路

增加通用提醒状态、数据库迁移和定时同步，覆盖风险时效、文件回执、项目里程碑、访视窗口与协作申请。

新增网页端和桌面端提醒中心、真实投递诊断与固定隐私通知正文，并补齐登录来源聚合、测试和说明文档。

backend/app/api/v1/visits.py

@@ -12,6 +12,7 @@ from app.crud import study as study_crud
 from app.crud import visit as visit_crud
 from app.schemas.subject import SubjectUpdate
 from app.schemas.visit import EarlyTerminationCreate, VisitCreate, VisitRead, VisitUpdate
+from app.services import notification_service
 
 router = APIRouter()
 
@@ -42,6 +43,17 @@ async def _ensure_subject_active(db: AsyncSession, subject) -> None:
         raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="中心已停用")
 
 
+async def _resolve_visit_reminders(db: AsyncSession, visit_ids: list[uuid.UUID]) -> None:
+    for visit_id in set(visit_ids):
+        await notification_service.resolve_source_notifications(
+            db,
+            source_type="SUBJECT_VISIT_WINDOW",
+            source_id=str(visit_id),
+        )
+    if visit_ids:
+        await db.commit()
+
+
 @router.get(
     "/",
     response_model=list[VisitRead],
@@ -145,6 +157,8 @@ async def create_early_termination(
     if subject.baseline_date and termination_in.termination_date < subject.baseline_date:
         raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail="提前终止日期不能早于基线/治疗日期")
 
+    existing_visit_ids = [visit.id for visit in await visit_crud.list_visits(db, subject_id)]
+
     try:
         visit = await visit_crud.create_early_termination_visit(
             db,
@@ -164,6 +178,7 @@ async def create_early_termination(
             drop_reason=reason,
         ),
     )
+    await _resolve_visit_reminders(db, existing_visit_ids)
     await audit_crud.log_action(
         db,
         study_id=study_id,
@@ -209,6 +224,8 @@ async def update_visit(
     old_status = visit.status
     updated = await visit_crud.update_visit(db, visit, visit_in)
     await subject_crud.sync_subject_status(db, subject)
+    if updated.actual_date is not None or updated.status in {"DONE", "CANCELLED"}:
+        await _resolve_visit_reminders(db, [updated.id])
     detail = None
     if visit_in.status:
         detail = json.dumps(
@@ -253,6 +270,7 @@ async def delete_visit(
     visit_detail = _visit_audit_detail("删除", subject, visit)
     await visit_crud.delete_visit(db, visit)
     await subject_crud.sync_subject_status(db, subject)
+    await _resolve_visit_reminders(db, [visit_id])
     await audit_crud.log_action(
         db,
         study_id=study_id,