refactor: migrate to eslint flat config and format codebase with prettier

- Remove legacy .eslintrc.cjs and .eslintignore
- Add eslint.config.js with flat config, security rules (no-eval, no-implied-eval, no-new-func, no-script-url)
- Add .prettierrc and .prettierignore
- Format entire codebase with prettier

src/locales/zh.json

@@ -933,4 +933,4 @@
       "checkError": "检查失败。请稍后重试。"
     }
   }
-}
+}