* fix(config): spell out and pluralize refresh interval units

The usage refresh presets ("1 min" ... "15 min") and the custom interval suffix ("%1 s") now use plural-aware whole words, reusing the existing translated "%1 minute"/"%1 minutes" message and adding "%1 second"/"%1 seconds" in every catalog. This matches the "Check every" hours field and the KDE HIG units guidance.

Opened by PlasmaPolish

* docs(config): update valueFromText comment for plural seconds label