fix(design): the table header takes the B9 fade utility, and every size is dvh, not vh (E28 S3d4)

The table header carried an arbitrary-value copy of fade-below; a contract refuses a hand gradient of a surface colour. 100vh is the viewport with a tablet browser's toolbar retracted, so h-screen / min-h-screen / static vh hid the last rows under it; a contract holds dvh (the Plex player stage changes with S3f, where it is played on the tablet).

frontend/src/components/BootGate.tsx

@@ -30,7 +30,7 @@ import { LoadingState, StateMessage } from "./ui/QueryState";
  * Suspense fallback after it and the first page's own loading state keep one clock (see LoadingState). */
 export function BootScreen() {
   return (
-    <div className="min-h-screen grid place-items-center">
+    <div className="min-h-dvh grid place-items-center">
       <LoadingState since={0} delayMs={400} />
     </div>
   );
@@ -121,7 +121,7 @@ export default function BootGate({ children }: { children: ReactNode }) {
         : null;
   if (failed)
     return (
-      <div className="min-h-screen grid place-items-center">
+      <div className="min-h-dvh grid place-items-center">
         <StateMessage tone="error" onRetry={() => failed.refetch()}>
           {t("common.somethingWrong")}
         </StateMessage>