fix: Enhance file type detection in HTTP Request node

[tancheng33]

Summary

Enhances file type detection in the HTTP Request node by improving MIME type detection logic. The changes include:

1. Added fallback mechanism for content type detection:

   • First tries Content-Type from response headers
   • Then attempts to guess type from URL using mimetypes
   • Finally defaults to "application/octet-stream" if no type can be determined

2. Improved file handling in HTTP responses by properly checking both Content-Type headers and URL patterns

This change ensures more reliable file type detection when handling HTTP responses, particularly for file downloads where the Content-Type header might be missing or incorrect.

close #11459

Screenshots

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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

[crazywoola]

Please fix the lint error, maybe you need to rebase the origin/main.