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/log.ts

@@ -1,4 +1,4 @@
-export type LogAnnotation = {
+export interface LogAnnotation {
   content: string
   account: {
     id: string
@@ -8,7 +8,7 @@ export type LogAnnotation = {
   created_at: number
 }
 
-export type Annotation = {
+export interface Annotation {
   id: string
   authorName: string
   logAnnotation?: LogAnnotation