feat(plugin): 循环引用检测 — no_cycle 字段支持

新增 check_no_cycle 异步函数，通过沿 parent 链上溯检测
是否存在循环引用。在 update 方法中集成，对声明 no_cycle
的字段执行检测，最多遍历 100 层防止无限循环。

crates/erp-plugin/src/data_service.rs

@@ -209,6 +209,13 @@ impl PluginDataService {
         validate_data(&data, &fields)?;
         validate_ref_entities(&data, &fields, entity_name, plugin_id, tenant_id, db, false, Some(id)).await?;
 
+        // 循环引用检测
+        for field in &fields {
+            if field.no_cycle == Some(true) && data.get(&field.name).is_some() {
+                check_no_cycle(id, field, &data, &info.table_name, tenant_id, db).await?;
+            }
+        }
+
         let (sql, values) = DynamicTableManager::build_update_sql(
             &info.table_name,
             id,
@@ -576,6 +583,62 @@ async fn validate_ref_entities(
     Ok(())
 }
 
+/// 循环引用检测 — 用于 no_cycle 字段
+async fn check_no_cycle(
+    record_id: Uuid,
+    field: &PluginField,
+    data: &serde_json::Value,
+    table_name: &str,
+    tenant_id: Uuid,
+    db: &sea_orm::DatabaseConnection,
+) -> AppResult<()> {
+    let Some(val) = data.get(&field.name) else { return Ok(()) };
+    let new_parent = val.as_str().unwrap_or("").trim().to_string();
+    if new_parent.is_empty() { return Ok(()); }
+
+    let new_parent_id = Uuid::parse_str(&new_parent).map_err(|_| {
+        AppError::Validation("parent_id 不是有效的 UUID".to_string())
+    })?;
+
+    let field_name = sanitize_identifier(&field.name);
+    let mut visited = vec![record_id];
+    let mut current_id = new_parent_id;
+
+    for _ in 0..100 {
+        if visited.contains(&current_id) {
+            let label = field.display_name.as_deref().unwrap_or(&field.name);
+            return Err(AppError::Validation(format!(
+                "字段 '{}' 形成循环引用", label
+            )));
+        }
+        visited.push(current_id);
+
+        let query_sql = format!(
+            "SELECT data->>'{}' as parent FROM \"{}\" WHERE id = $1 AND tenant_id = $2 AND deleted_at IS NULL",
+            field_name, table_name
+        );
+        #[derive(FromQueryResult)]
+        struct ParentRow { parent: Option<String> }
+        let row = ParentRow::find_by_statement(Statement::from_sql_and_values(
+            sea_orm::DatabaseBackend::Postgres,
+            query_sql,
+            [current_id.into(), tenant_id.into()],
+        )).one(db).await?;
+
+        match row {
+            Some(r) => {
+                let parent = r.parent.unwrap_or_default().trim().to_string();
+                if parent.is_empty() { break; }
+                current_id = Uuid::parse_str(&parent).map_err(|_| {
+                    AppError::Internal("parent_id 不是有效的 UUID".to_string())
+                })?;
+            }
+            None => break,
+        }
+    }
+    Ok(())
+}
+
 #[cfg(test)]
 mod validate_tests {
     use super::*;