feat(editor): Add support for changing sticky notes color in new canvas (no-changelog)

[alexgrozav]

Summary

https://github.com/user-attachments/assets/7b6b0cb1-c333-4471-b9b3-ad94aa3c08d1

Related Linear tickets, Github issues, and Community forum posts

https://linear.app/n8n/issue/N8N-7507/as-a-user-i-want-to-be-able-to-change-sticky-note-colors

Review / Merge checklist

• [x] PR title and summary are descriptive. (conventions)
• [ ] Docs updated or follow-up ticket created.
• [x] Tests included.
• [ ] PR Labeled with release/backport (if the PR is an urgent fix that needs to be backported)