feat: initialize Nuanji (Warm Notes) project

- Base platform from base.git (ERP base: auth, core, config, message, workflow, plugin)
- Created erp-diary module skeleton (lib.rs, dto.rs, error.rs, event.rs, state.rs)
- Integrated erp-diary into workspace and erp-server
- Added DiaryModule registration in main.rs
- Added DiaryState FromRef in state.rs
- Diary routes mounted (empty routes, ready for implementation)
- Product design spec v1.2 preserved in docs/
- Implementation plan preserved in plans/

Cargo check: OK
Cargo test: OK (78+ base tests passing)

crates/erp-server/src/tasks.rs

@@ -0,0 +1,125 @@
+use std::sync::atomic::{AtomicU64, Ordering};
+use std::sync::Arc;
+use std::time::Duration;
+
+fn touch_heartbeat(heartbeat: &Arc<AtomicU64>) {
+    let now = std::time::SystemTime::now()
+        .duration_since(std::time::UNIX_EPOCH)
+        .unwrap_or_default()
+        .as_secs();
+    heartbeat.store(now, Ordering::Relaxed);
+}
+
+/// 启动事件清理后台任务。
+///
+/// 每日执行一次：
+/// - 调用 `cleanup_old_published_events()` 归档 >7 天的已发布事件
+/// - 调用 `cleanup_old_processed_events()` 清理 >7 天的去重记录
+pub fn start_event_cleanup(db: sea_orm::DatabaseConnection, heartbeat: Arc<AtomicU64>) {
+    tokio::spawn(async move {
+        let mut interval = tokio::time::interval(Duration::from_secs(86400));
+        loop {
+            interval.tick().await;
+            if let Err(e) = run_cleanup(&db).await {
+                tracing::warn!(error = %e, "事件清理任务执行失败");
+            }
+            touch_heartbeat(&heartbeat);
+        }
+    });
+    tracing::info!("事件清理任务已启动（每 24 小时执行一次）");
+}
+
+async fn run_cleanup(db: &sea_orm::DatabaseConnection) -> Result<(), sea_orm::DbErr> {
+    use sea_orm::ConnectionTrait;
+
+    // 归档 >7 天的已发布事件
+    match db
+        .execute_unprepared("SELECT cleanup_old_published_events(7, 1000)")
+        .await
+    {
+        Ok(result) => {
+            tracing::info!(rows_affected = result.rows_affected(), "已发布事件归档完成");
+        }
+        Err(e) => tracing::warn!(error = %e, "已发布事件归档失败"),
+    }
+
+    // 清理 >7 天的去重记录
+    match db
+        .execute_unprepared("SELECT cleanup_old_processed_events(7, 1000)")
+        .await
+    {
+        Ok(result) => {
+            tracing::info!(rows_affected = result.rows_affected(), "去重记录清理完成");
+        }
+        Err(e) => tracing::warn!(error = %e, "去重记录清理失败"),
+    }
+
+    Ok(())
+}
+
+/// 启动 DB 连接池 + EventBus 积压指标采样任务。
+///
+/// 每 30 秒采样一次并导出为 Prometheus gauge：
+/// - `db_pool_connections_active` — 当前活跃连接数
+/// - `db_pool_connections_idle` — 当前空闲连接数
+/// - `eventbus_pending_total` — pending 状态的领域事件数
+pub fn start_pool_metrics(db: sea_orm::DatabaseConnection, heartbeat: Arc<AtomicU64>) {
+    tokio::spawn(async move {
+        let mut interval = tokio::time::interval(Duration::from_secs(30));
+        loop {
+            interval.tick().await;
+            sample_pool_metrics(&db).await;
+            sample_eventbus_backlog(&db).await;
+            touch_heartbeat(&heartbeat);
+        }
+    });
+    tracing::info!("DB 连接池 + EventBus 积压指标采样已启动（每 30 秒采样一次）");
+}
+
+async fn sample_pool_metrics(db: &sea_orm::DatabaseConnection) {
+    use sea_orm::FromQueryResult;
+
+    #[derive(FromQueryResult)]
+    struct CountRow {
+        cnt: i64,
+    }
+
+    // 通过 pg_stat_activity 查询当前连接数
+    let stmt = sea_orm::Statement::from_string(
+        sea_orm::DatabaseBackend::Postgres,
+        "SELECT COUNT(*)::bigint AS cnt FROM pg_stat_activity WHERE state = 'active'".to_string(),
+    );
+    if let Ok(Some(row)) = CountRow::find_by_statement(stmt).one(db).await {
+        metrics::gauge!("db_pool_connections_active").set(row.cnt as f64);
+    }
+
+    let stmt = sea_orm::Statement::from_string(
+        sea_orm::DatabaseBackend::Postgres,
+        "SELECT COUNT(*)::bigint AS cnt FROM pg_stat_activity WHERE state = 'idle'".to_string(),
+    );
+    if let Ok(Some(row)) = CountRow::find_by_statement(stmt).one(db).await {
+        metrics::gauge!("db_pool_connections_idle").set(row.cnt as f64);
+    }
+}
+
+async fn sample_eventbus_backlog(db: &sea_orm::DatabaseConnection) {
+    use sea_orm::FromQueryResult;
+
+    #[derive(FromQueryResult)]
+    struct CountRow {
+        cnt: i64,
+    }
+
+    let stmt = sea_orm::Statement::from_string(
+        sea_orm::DatabaseBackend::Postgres,
+        "SELECT COUNT(*)::bigint AS cnt FROM domain_events WHERE status = 'pending'".to_string(),
+    );
+    match CountRow::find_by_statement(stmt).one(db).await {
+        Ok(Some(row)) => {
+            metrics::gauge!("eventbus_pending_total").set(row.cnt as f64);
+        }
+        _ => {
+            tracing::debug!("EventBus 积压采样：无法获取 pending 事件数");
+        }
+    }
+}