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>

utils/tools.ts

@@ -2,18 +2,15 @@ import type { ThoughtItem } from '@/app/components/chat/type'
 import type { VisionFile } from '@/types/app'
 
 export const sortAgentSorts = (list: ThoughtItem[]) => {
-  if (!list)
-    return list
-  if (list.some(item => item.position === undefined))
-    return list
+  if (!list) { return list }
+  if (list.some(item => item.position === undefined)) { return list }
   const temp = [...list]
   temp.sort((a, b) => a.position - b.position)
   return temp
 }
 
 export const addFileInfos = (list: ThoughtItem[], messageFiles: VisionFile[]) => {
-  if (!list || !messageFiles)
-    return list
+  if (!list || !messageFiles) { return list }
   return list.map((item) => {
     if (item.files && item.files?.length > 0) {
       return {