feat: migrate ESLint to v9 flat config

- Replace .eslintrc.json with eslint.config.mjs
- Simplify configuration using @antfu/eslint-config
- Add necessary ESLint plugin dependencies
- Disable overly strict style rules
- Set package.json type to module for ESM support
- Fix ESLint disable comment format

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

types/base.ts

@@ -1,5 +1,5 @@
-export type TypeWithI18N<T = string> = {
-  'en_US': T
-  'zh_Hans': T
+export interface TypeWithI18N<T = string> {
+  en_US: T
+  zh_Hans: T
   [key: string]: T
 }