Fix vertical alignment of DNS Mode dropdown in jail config

Add alignItems: "end" to the fieldRow grid style so that all grid
cells align their content to the bottom edge of the row. This ensures
the DNS Mode <Select> and the Date Pattern <Combobox> sit on the same
horizontal baseline even though Date Pattern carries a hint line that
makes it taller.

All other fieldRow usages have consistent hint presence across their
fields, so no visual regressions are introduced.

frontend/src/components/config/configStyles.ts

@@ -129,6 +129,7 @@ export const useConfigStyles = makeStyles({
     gridTemplateColumns: "1fr 1fr",
     gap: tokens.spacingHorizontalM,
     marginBottom: tokens.spacingVerticalS,
+    alignItems: "end",
     "@media (max-width: 900px)": {
       gridTemplateColumns: "1fr",
     },