refactor: entries + secrets 双表，search 展示 field schema，key_ref PEM 共享

- secrets 表拆为 entries（主表）+ secrets（每字段一行）
- search 无需 master_key 即可展示 secrets 字段名、类型、长度
- inject/run 支持 metadata.key_ref 引用 kind=key 记录，PEM 轮换 O(1)
- entries_history + secrets_history 字段级历史，rollback 按 version 恢复
- 移除迁移用 DROP 语句，migrate 幂等
- v0.8.0

Made-with: Cursor

Cargo.lock

@@ -1836,7 +1836,7 @@ checksum = "94143f37725109f92c262ed2cf5e59bce7498c01bcc1502d7b9afe439a4e9f49"
 
 [[package]]
 name = "secrets"
-version = "0.7.5"
+version = "0.8.0"
 dependencies = [
  "aes-gcm",
  "anyhow",