Remove large advertisement from homepage below carousel

Removes the `ArticleCardAd` component from the home page (`client/src/pages/home.tsx`) to eliminate a large advertisement positioned directly below the carousel. Also updates image URLs in `server/gallery-data.json` to new Dropbox locations.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: 1f7e7e89-a520-4970-9645-37daadc466dc
Replit-Commit-Checkpoint-Type: full_checkpoint
Replit-Commit-Event-Id: d8db5fc6-0476-4950-ae0c-7bc1341fd856
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client/src/pages/home.tsx

@@ -679,8 +679,6 @@ export default function Home() {
           </div>
         </div>
 
-        <ArticleCardAd />
-
         {widePickedArticles.length > 0 && (
           <div className="grid grid-cols-1 sm:grid-cols-2 gap-4">
             {widePickedArticles.map((a) => (