fix: update default.conf.template avoid embed.min.js 404

[n2em]

Summary

After update to latest version the external embed app does not work, console in browser show that embed.min.js in 404 status.

Close #14077

Screenshots

Before	After
can not access embed.min.js external	external embed app works well

Checklist

Important

Please review the checklist below before submitting your pull request.

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods