feat: 增强SaaS后端功能与安全性

refactor: 重构数据库连接使用PostgreSQL替代SQLite
feat(auth): 增加JWT验证的audience和issuer检查
feat(crypto): 添加AES-256-GCM字段加密支持
feat(api): 集成utoipa实现OpenAPI文档
fix(admin): 修复配置项表单验证逻辑
style: 统一代码格式与类型定义
docs: 更新技术栈文档说明PostgreSQL

Cargo.toml

@@ -57,7 +57,7 @@ chrono = { version = "0.4", features = ["serde"] }
 uuid = { version = "1", features = ["v4", "v5", "serde"] }
 
 # Database
-sqlx = { version = "0.7", features = ["runtime-tokio", "sqlite"] }
+sqlx = { version = "0.7", features = ["runtime-tokio", "postgres", "chrono"] }
 libsqlite3-sys = { version = "0.27", features = ["bundled"] }
 
 # HTTP client (for LLM drivers)