refactor(backend): update supporting modules for database compatibility

- Add DatabaseError variant to AppError enum
- Update provider module to support database-backed operations
- Modify codex_config to work with new database structure
- Ensure error handling covers database operations

src-tauri/src/error.rs

@@ -50,6 +50,8 @@ pub enum AppError {
         zh: String,
         en: String,
     },
+    #[error("数据库错误: {0}")]
+    Database(String),
 }
 
 impl AppError {