refactor: 消除冗余、统一设计，bump 0.9.1

- 提取 EntryRow/SecretFieldRow 到 models.rs
- 提取 current_actor()、print_json() 公共函数
- ExportFormat::from_extension 复用 from_str
- fetch_entries 默认 limit 100k（export/inject/run 不再截断）
- history 独立为 history.rs 模块
- delete 改用 DeleteArgs 结构体
- config_dir 改为 Result，Argon2id 参数提取常量
- Cargo 依赖 ^ 前缀、tokio 精简 features
- 更新 AGENTS.md 项目结构

Made-with: Cursor

src/db.rs

@@ -3,6 +3,8 @@ use serde_json::Value;
 use sqlx::PgPool;
 use sqlx::postgres::PgPoolOptions;
 
+use crate::audit::current_actor;
+
 pub async fn create_pool(database_url: &str) -> Result<PgPool> {
     tracing::debug!("connecting to database");
     let pool = PgPoolOptions::new()
@@ -139,7 +141,7 @@ pub async fn snapshot_entry_history(
     tx: &mut sqlx::Transaction<'_, sqlx::Postgres>,
     p: EntrySnapshotParams<'_>,
 ) -> Result<()> {
-    let actor = std::env::var("USER").unwrap_or_default();
+    let actor = current_actor();
     sqlx::query(
         "INSERT INTO entries_history \
          (entry_id, namespace, kind, name, version, action, tags, metadata, actor) \
@@ -177,7 +179,7 @@ pub async fn snapshot_secret_history(
     tx: &mut sqlx::Transaction<'_, sqlx::Postgres>,
     p: SecretSnapshotParams<'_>,
 ) -> Result<()> {
-    let actor = std::env::var("USER").unwrap_or_default();
+    let actor = current_actor();
     sqlx::query(
         "INSERT INTO secrets_history \
          (entry_id, secret_id, entry_version, field_name, field_type, value_len, encrypted, action, actor) \