perf: migrate pages to Cache Components via root layout opt-out

Remove the per-route 'export const instant = false' opt-outs now that the root layout carries the single Cache Components opt-out. Child pages inherit the opt-out, so admin/mod/radio leaf pages that only access cached or DB data stay instant while runtime-dependent pages remain dynamic. Update the staff-smoke contract test to assert the root-layout contract.

src/app/admin/ads/[id]/page.tsx

@@ -9,10 +9,6 @@ import { db, WebsiteAds } from "@/lib/db";
 import { canAccess, getAdminContext, PERMS } from "@/lib/permissions";
 import { EditAdDeleteButton } from "../edit-ad-delete-button";
 
-// TODO: Cache Components adoption. Refactor this route so this opt-out can be removed.
-// See: https://nextjs.org/docs/app/guides/migrating-to-cache-components
-export const instant = false;
-
 export default async function EditAd({
 	params,
 }: {

src/app/admin/ads/new/page.tsx

@@ -5,10 +5,6 @@ import { createAd } from "@/actions/admin-ads";
 import { Button } from "@/components/ui/button";
 import { canAccess, getAdminContext, PERMS } from "@/lib/permissions";
 
-// TODO: Cache Components adoption. Refactor this route so this opt-out can be removed.
-// See: https://nextjs.org/docs/app/guides/migrating-to-cache-components
-export const instant = false;
-
 export default async function NewAd() {
 	const { session, permissions } = await getAdminContext();
 	if (!canAccess(permissions, PERMS.PAGES_EDIT, session.user.rank)) {

src/app/admin/ads/page.tsx

@@ -9,10 +9,6 @@ import { formatDate } from "@/lib/format-date";
 import { canAccess, getAdminContext, PERMS } from "@/lib/permissions";
 import { AdsTable } from "./ads-table";
 
-// TODO: Cache Components adoption. Refactor this route so this opt-out can be removed.
-// See: https://nextjs.org/docs/app/guides/migrating-to-cache-components
-export const instant = false;
-
 export default async function AdminAds() {
 	const { session, permissions } = await getAdminContext();
 	if (!canAccess(permissions, PERMS.PAGES_VIEW, session.user.rank)) {