style: add color to dashboard workflow stats cards

[Nic13Gamer]

Summary

This PR adds some color to the background and border of the workflow stat cards. I think it makes it faster/easier to skim through and find the info you need.

Changes

• Added class with color class-names to stats array in <WorkflowStats />

Observations

I also tried adding color to the icons, but found it too much, let me know if you would like it though.

Also removed the border- color classes from the card. Apparently shadcn/ui now uses ring- for the card primitive, I don't know why not use border though, to be honest.

[Copilot]

Pull request overview

This PR enhances the visual design of workflow statistics cards by adding semantic color coding to differentiate between different workflow states. Each status card now has a subtle colored background and ring border that matches its semantic meaning (e.g., warning for pending, success for completed, destructive for failed).

Changes:

• Added optional class property to workflow stats array with semantic color classes for background and ring borders
• Refactored className construction to use the cn utility instead of template strings
• Removed deprecated border classes in favor of ring classes that align with the Card component's defaults

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