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-server/migration/src/lib.rs

@@ -30,6 +30,7 @@ mod m20260414_000027_fix_unique_indexes_soft_delete;
 mod m20260414_000028_add_standard_fields_to_tokens;
 mod m20260414_000029_add_standard_fields_to_process_variables;
 mod m20260415_000030_add_version_to_message_tables;
+mod m20260416_000031_create_domain_events;
 
 pub struct Migrator;
 
@@ -67,6 +68,7 @@ impl MigratorTrait for Migrator {
             Box::new(m20260414_000028_add_standard_fields_to_tokens::Migration),
             Box::new(m20260414_000029_add_standard_fields_to_process_variables::Migration),
             Box::new(m20260415_000030_add_version_to_message_tables::Migration),
+            Box::new(m20260416_000031_create_domain_events::Migration),
         ]
     }
 }

crates/erp-server/migration/src/m20260416_000031_create_domain_events.rs

@@ -0,0 +1,80 @@
+use sea_orm_migration::prelude::*;
+
+#[derive(DeriveMigrationName)]
+pub struct Migration;
+
+#[async_trait::async_trait]
+impl MigrationTrait for Migration {
+    async fn up(&self, manager: &SchemaManager) -> Result<(), DbErr> {
+        manager
+            .create_table(
+                Table::create()
+                    .table(Alias::new("domain_events"))
+                    .if_not_exists()
+                    .col(
+                        ColumnDef::new(Alias::new("id"))
+                            .uuid()
+                            .not_null()
+                            .primary_key(),
+                    )
+                    .col(ColumnDef::new(Alias::new("tenant_id")).uuid().not_null())
+                    .col(ColumnDef::new(Alias::new("event_type")).string_len(200).not_null())
+                    .col(ColumnDef::new(Alias::new("payload")).json().null())
+                    .col(ColumnDef::new(Alias::new("correlation_id")).uuid().null())
+                    .col(
+                        ColumnDef::new(Alias::new("status"))
+                            .string_len(20)
+                            .not_null()
+                            .default("pending"),
+                    )
+                    .col(
+                        ColumnDef::new(Alias::new("attempts"))
+                            .integer()
+                            .not_null()
+                            .default(0),
+                    )
+                    .col(ColumnDef::new(Alias::new("last_error")).text().null())
+                    .col(
+                        ColumnDef::new(Alias::new("created_at"))
+                            .timestamp_with_time_zone()
+                            .not_null(),
+                    )
+                    .col(
+                        ColumnDef::new(Alias::new("published_at"))
+                            .timestamp_with_time_zone()
+                            .null(),
+                    )
+                    .to_owned(),
+            )
+            .await?;
+
+        manager
+            .create_index(
+                Index::create()
+                    .name("idx_domain_events_status")
+                    .table(Alias::new("domain_events"))
+                    .col(Alias::new("status"))
+                    .col(Alias::new("created_at"))
+                    .to_owned(),
+            )
+            .await?;
+
+        manager
+            .create_index(
+                Index::create()
+                    .name("idx_domain_events_tenant")
+                    .table(Alias::new("domain_events"))
+                    .col(Alias::new("tenant_id"))
+                    .to_owned(),
+            )
+            .await?;
+
+        Ok(())
+    }
+
+    async fn down(&self, manager: &SchemaManager) -> Result<(), DbErr> {
+        manager
+            .drop_table(Table::drop().table(Alias::new("domain_events")).to_owned())
+            .await
+    }
+}