fix(health): 修复工作台统计 SQL 表名 — alerts/follow_up_task

- alert → alerts（实际表名复数）
- follow_up_plan → follow_up_task（表不存在，改用 pending 状态的随访任务）

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

@@ -490,7 +490,7 @@ pub async fn get_workbench_stats(
     let urgent_alerts: i64 = FromQueryResult::find_by_statement(
         Statement::from_sql_and_values(
             DatabaseBackend::Postgres,
-            "SELECT COUNT(*) AS cnt FROM alert WHERE tenant_id = $1 AND severity = 'urgent' AND status = 'active' AND deleted_at IS NULL",
+            "SELECT COUNT(*) AS cnt FROM alerts WHERE tenant_id = $1 AND severity = 'urgent' AND status = 'active' AND deleted_at IS NULL",
             [tenant_id.into()],
         ),
     )
@@ -503,7 +503,7 @@ pub async fn get_workbench_stats(
     let followup_due: i64 = FromQueryResult::find_by_statement(
         Statement::from_sql_and_values(
             DatabaseBackend::Postgres,
-            "SELECT COUNT(*) AS cnt FROM follow_up_plan WHERE tenant_id = $1 AND status = 'scheduled' AND next_date <= NOW() AND deleted_at IS NULL",
+            "SELECT COUNT(*) AS cnt FROM follow_up_task WHERE tenant_id = $1 AND status = 'pending' AND deleted_at IS NULL",
             [tenant_id.into()],
         ),
     )