ads: drop IntersectionObserver gate — one mount = one impression

src/components/AdImage.tsx

@@ -53,30 +53,13 @@ export default function AdImage({
     const id = ad.campaign_id || ad.slug;
     if (!id) return;
 
+    // One impression per pageview per banner, fired on mount. No viewport
+    // gate — too many ad slots sit below-the-fold and the IO threshold
+    // suppressed real signal.
     if (!beaconMount.current) {
       beaconMount.current = true;
       sendImpression(id, page, false);
     }
-
-    const el = containerRef.current;
-    if (!el) return;
-
-    const observer = new IntersectionObserver(
-      (entries) => {
-        for (const e of entries) {
-          if (e.isIntersecting) {
-            const now = Date.now();
-            if (now - lastViewportFire.current >= 12000) {
-              lastViewportFire.current = now;
-              sendImpression(id, page, true);
-            }
-          }
-        }
-      },
-      { threshold: 0.5 },
-    );
-    observer.observe(el);
-    return () => observer.disconnect();
   }, [ad.src, ad.slug, ad.campaign_id, page]);
 
   if (!ad.src) return null;