fix: add animation to workflow process loader icon

[DDDDD12138]

Summary

Running workflows lacked a loading state indicator. This PR addresses the issue by adding an animate-spin class to the loader icon, providing users with clear visual feedback of workflow execution status.

Close #15505

Screenshots

Before

eryKBE7kfu.mp4

After

zT2xKVeDHw.mp4

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