perf: cut cold route compilation and unblock preview images (#6441)

packages/api/src/server-settings-server.ts

@@ -0,0 +1,8 @@
+import { cache } from "react";
+
+import { db } from "@homarr/db";
+import { getServerSettingsAsync } from "@homarr/db/queries";
+
+// One settings snapshot per RSC request, shared by the root layout, theme, and
+// widget prefetching. React invalidates this cache between requests.
+export const getRscServerSettingsAsync = cache(async () => await getServerSettingsAsync(db));