lib/ads: drop in-process cache 5min → 30s

Pairs with advertising-rmp's /api/banners cache shortening so admin
banner uploads appear on the live site in ~60s instead of up to 15min.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/ads.ts

@@ -25,7 +25,11 @@ const SUPABASE_URL = process.env.NEXT_PUBLIC_SUPABASE_URL!;
 const SUPABASE_ANON = process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!;
 const SCHEMA = process.env.NEXT_PUBLIC_SUPABASE_SCHEMA || "bb";
 
-const CACHE_TTL_MS = 5 * 60 * 1000;
+// 30s in-process cache so admin uploads show on the site within ~30s.
+// The /api/banners endpoint also caps at 30s, so worst-case from upload
+// to live is ~60s. Was 5min, which combined with the API + CDN layers
+// could push banner updates out to 15 minutes.
+const CACHE_TTL_MS = 30 * 1000;
 type CacheRow = { rows: Ad[]; loadedAt: number };
 let CACHE: CacheRow | null = null;
 let REFRESH_IN_FLIGHT: Promise<void> | null = null;
@@ -94,7 +98,7 @@ interface RmpBanner {
 async function fetchPlacement(size: Ad["size"]): Promise<Ad[]> {
   try {
     const res = await fetch(`${RMP_API}/api/banners/${PROPERTY}/${size}`, {
-      next: { revalidate: 300 },
+      next: { revalidate: 30 },
     });
     if (!res.ok) return [];
     const data = await res.json() as { banners?: RmpBanner[] };