feat(core): implement event outbox persistence

Add domain_events migration and SeaORM entity. Modify EventBus::publish
to persist events before broadcasting (best-effort: DB failure logs
warning but still broadcasts in-memory). Update all 19 publish call
sites across 4 crates to pass db reference.

Add outbox relay background task that polls pending events every 5s
and re-broadcasts them, ensuring no events are lost on server restart.

crates/erp-core/src/entity/domain_event.rs

@@ -0,0 +1,24 @@
+use sea_orm::entity::prelude::*;
+use serde::{Deserialize, Serialize};
+
+/// 领域事件实体 — 映射 domain_events 表。
+#[derive(Clone, Debug, PartialEq, DeriveEntityModel, Serialize, Deserialize)]
+#[sea_orm(table_name = "domain_events")]
+pub struct Model {
+    #[sea_orm(primary_key, auto_increment = false)]
+    pub id: Uuid,
+    pub tenant_id: Uuid,
+    pub event_type: String,
+    pub payload: Option<serde_json::Value>,
+    pub correlation_id: Option<Uuid>,
+    pub status: String,
+    pub attempts: i32,
+    pub last_error: Option<String>,
+    pub created_at: DateTimeUtc,
+    pub published_at: Option<DateTimeUtc>,
+}
+
+#[derive(Copy, Clone, Debug, EnumIter, DeriveRelation)]
+pub enum Relation {}
+
+impl ActiveModelBehavior for ActiveModel {}

crates/erp-core/src/entity/mod.rs

@@ -1 +1,2 @@
 pub mod audit_log;
+pub mod domain_event;