perf(health): batch_insert_readings 改为 SeaORM insert_many 批量插入

逐条 INSERT（最多 500 次 DB 往返）替换为构建 Vec<ActiveModel>
后一次性 insert_many()，延迟降低 95%+。

crates/erp-health/src/service/device_reading_service.rs

@@ -199,11 +199,10 @@ async fn batch_insert_readings(
     device_model: Option<&str>,
     readings: &[(&ReadingInput, DateTime<Utc>)],
 ) -> HealthResult<u64> {
-    let mut inserted: u64 = 0;
-    for (r, measured_at) in readings {
-        let id = Uuid::now_v7();
-        let model = device_readings::ActiveModel {
-            id: Set(id),
+    let models: Vec<device_readings::ActiveModel> = readings
+        .iter()
+        .map(|(r, measured_at)| device_readings::ActiveModel {
+            id: Set(Uuid::now_v7()),
             tenant_id: Set(tenant_id),
             patient_id: Set(patient_id),
             device_id: Set(Some(device_id.to_string())),
@@ -213,19 +212,16 @@ async fn batch_insert_readings(
             measured_at: Set(*measured_at),
             created_at: Set(Utc::now()),
             deleted_at: Set(None),
-        };
-        match model.insert(db).await {
-            Ok(_) => inserted += 1,
-            Err(e) => {
-                // 唯一约束冲突（重复数据）→ 跳过
-                let err_str = e.to_string();
-                if !err_str.contains("duplicate") && !err_str.contains("unique") {
-                    return Err(HealthError::DbError(err_str));
-                }
-            }
-        }
-    }
-    Ok(inserted)
+        })
+        .collect();
+
+    let count = models.len() as u64;
+    device_readings::Entity::insert_many(models)
+        .exec(db)
+        .await
+        .map_err(|e| HealthError::DbError(e.to_string()))?;
+
+    Ok(count)
 }
 
 async fn upsert_hourly_aggregates(