fix: return absolute path as the icon url if CONSOLE_API_URL is empty

[kurokobo]

Summary

This is follow-up for #15241 by @crazywoola and @zhangxl01.

• Reverts fix: tool icons are missing #15241
• Change API to solve the issue
• Add test cases for yarl.URL

The PR #15241 solves the issue by Nginx, but I think the issue should be solved by the API side.

The issue is fundamentally caused by the API returning a relative path (without leading /) as the icon URL when the CONSOLE_API_URL is empty.

If the specified URL does not start with /, the browser treats it as a relative path from the current URL. This causes 404 for all icons (See the screen shot below).

Simply ensuring that the API returns a path starting with / as the icon URL will resolve the issue, as the browser will interpret it as an absolute path from the root of the current domain.

Related #15189, #14668, #14835, #14570, #13982, #14835, #14578

Screenshots

Before	After

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]

Cool, this seems much better to me. One thing should be addressed that #15241 this can fix the tools are missing temporary, because this can be done by restarting the container. This fix requires to rebuild the image which won't be available until next version. :)

I will merge this later. @kurokobo