Gray out label for up/down/maintenance labels when they are zero

[j-f1]

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Description

Previously, the numbers in the Quick Stats panel were always displayed in color even if they were 0. This PR updates them to show up in gray unless they’re non-zero. This is particularly helpful for the “down” indicator since if you don’t see the red number you can be confident that none of your monitors are down.

Type of change

Please delete any options that are not relevant.

• User interface (UI)

Checklist

• My code follows the style guidelines of this project
• I ran ESLint and other linters for modified files
• I have performed a self-review of my own code and tested it
• I have commented my code, particularly in hard-to-understand areas
  (including JSDoc for methods) (N/A)
• My changes generate no new warnings
• My code needed automated testing. I have added them (this is optional task)

Screenshots (if any)

[CommanderStorm]

Thanks for the bugfix!
Forgot to write a merge message and merge the PR the last time around.

All changes in this PR are small and uncontroversial ⇒ merging with junior maintainer approval