Prevent date inputs shifting alignment on iPadOS

Due to an upstream issue in Safari on iPadOS 18 (and potentially 17), the box model calculations for these inputs go iffy when the value is deleted and re-typed.

The upstream issue was reported during the beta period of iPadOS 26 and fixed in the release of iPadOS 26 in September, however no fix for older versions seems to be coming, so we should prevent the issue in our own code in the meantime.

NHS.UK Frontend issue: nhsuk/nhsuk-frontend#1227
Our bug report: alphagov/reported-bugs#90

Author: querkmachine

packages/govuk-frontend/src/govuk/components/date-input/_index.scss

@@ -14,6 +14,11 @@
     display: inline-block;
     margin-right: govuk-spacing(4);
     margin-bottom: 0;
+
+    // Prevents an issue in Safari 18 on iPadOS where the inputs move up
+    // and down when values are deleted and retyped.
+    // https://github.com/alphagov/reported-bugs/issues/90
+    vertical-align: bottom;
   }
 
   .govuk-date-input__label {