* feat: add URL content extraction for AI diagram generation
* Changes made as recommended by Claude:
1. Added a request timeout to prevent server resources from being tied up (route.ts)
2. Implemented runtime validation for the API response shape (url-utils.ts)
3. Removed hardcoded English error messages and replaced them with localized strings (url-input-dialog.tsx)
4. Fixed the incorrect i18n namespace (changed from pdf.* to url.*) (url-input-dialog.tsx and en/ja/zh.json)
* chore: restore package.json and package-lock.json
* fix: use i18n strings for URL dialog error messages
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Co-authored-by: dayuan.jiang <jdy.toh@gmail.com>
