feat: 添加结构化日志与审计

- tracing + tracing-subscriber，全局 --verbose/-v 与 RUST_LOG 控制
- 新增 audit_log 表，add/update/delete 成功后自动写入审计记录
- 新增 src/audit.rs，审计失败仅 warn 不中断主流程
- 更新 README/AGENTS.md，补充 verbose、audit_log 说明
- .vscode/tasks.json 增加 verbose/update/audit 测试任务

Made-with: Cursor

src/commands/delete.rs

@@ -1,7 +1,10 @@
 use anyhow::Result;
+use serde_json::json;
 use sqlx::PgPool;
 
 pub async fn run(pool: &PgPool, namespace: &str, kind: &str, name: &str) -> Result<()> {
+    tracing::debug!(namespace, kind, name, "deleting record");
+
     let result =
         sqlx::query("DELETE FROM secrets WHERE namespace = $1 AND kind = $2 AND name = $3")
             .bind(namespace)
@@ -11,8 +14,10 @@ pub async fn run(pool: &PgPool, namespace: &str, kind: &str, name: &str) -> Resu
             .await?;
 
     if result.rows_affected() == 0 {
+        tracing::warn!(namespace, kind, name, "record not found for deletion");
         println!("Not found: [{}/{}] {}", namespace, kind, name);
     } else {
+        crate::audit::log(pool, "delete", namespace, kind, name, json!({})).await;
         println!("Deleted: [{}/{}] {}", namespace, kind, name);
     }
     Ok(())