feat(health): 班次管理与护士分配 — Shift/PatientAssignment/HandoffLog CRUD

- 新增 3 张数据表迁移 (shifts, patient_assignments, shift_handoff_log)
- 3 个 SeaORM Entity (shift, patient_assignment, handoff_log)
- 完整 CRUD 服务层：班次管理、患者分配（含批量分配）、交接记录
- 12 个 API 端点 + health.shifts.list/manage 权限
- 班次列表含患者分配摘要 (patient_count/critical_count/attention_count)
- 乐观锁、软删除、审计日志、事件发布
- 输入验证：period/shift_status/care_level 白名单

crates/erp-health/src/error.rs

@@ -92,6 +92,15 @@ pub enum HealthError {
     #[error("护理计划预后不存在")]
     CarePlanOutcomeNotFound,
 
+    #[error("班次不存在")]
+    ShiftNotFound,
+
+    #[error("患者分配不存在")]
+    PatientAssignmentNotFound,
+
+    #[error("交接记录不存在")]
+    HandoffLogNotFound,
+
     #[error("状态转换无效: {0}")]
     InvalidStatusTransition(String),
 
@@ -133,7 +142,10 @@ impl From<HealthError> for AppError {
             | HealthError::MedicationReminderNotFound
             | HealthError::CarePlanNotFound
             | HealthError::CarePlanItemNotFound
-            | HealthError::CarePlanOutcomeNotFound => AppError::NotFound(err.to_string()),
+            | HealthError::CarePlanOutcomeNotFound
+            | HealthError::ShiftNotFound
+            | HealthError::PatientAssignmentNotFound
+            | HealthError::HandoffLogNotFound => AppError::NotFound(err.to_string()),
             HealthError::ScheduleFull => AppError::Validation(err.to_string()),
             HealthError::InvalidStatusTransition(s) => AppError::Validation(s),
             HealthError::VersionMismatch => AppError::VersionMismatch,