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>

hooks/use-breakpoints.ts

@@ -10,10 +10,8 @@ export enum MediaType {
 const useBreakpoints = () => {
   const [width, setWidth] = React.useState(globalThis.innerWidth)
   const media = (() => {
-    if (width <= 640)
-      return MediaType.mobile
-    if (width <= 768)
-      return MediaType.tablet
+    if (width <= 640) { return MediaType.mobile }
+    if (width <= 768) { return MediaType.tablet }
     return MediaType.pc
   })()
 

hooks/use-conversation.ts

@@ -30,8 +30,7 @@ function useConversation() {
   // input can be updated by user
   const [newConversationInputs, setNewConversationInputs] = useState<Record<string, any> | null>(null)
   const resetNewConversationInputs = () => {
-    if (!newConversationInputs)
-      return
+    if (!newConversationInputs) { return }
     setNewConversationInputs(produce(newConversationInputs, (draft) => {
       Object.keys(draft).forEach((key) => {
         draft[key] = ''