Featured to top, centered, capped; banner ads capped 728px centered; slot CTA

- Featured card moved to the top of Overview, centered, max 760px; the rotating
  link is capped to 728px and centered (banner-sized, not a huge block).
- Served banner creatives cap at min(100%,728px), centered — kills the oversized
  sample banner; ad slots center their creative + label.
- Featured self-sell: shows "N of C slots open today" + "Feature your link →"
  that jumps to Campaigns with Featured preselected.
- Campaign target/image/video URL fields get autocomplete=off and clear when the
  Campaigns pane opens, so no residual (e.g. massifly) URL carries over.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

public/wall.html

@@ -36,7 +36,7 @@
     </div>
   </div>
 </section>
-<script src="/assets/common.js?v=20260907m"></script>
+<script src="/assets/common.js?v=20260907n"></script>
 <script src="/assets/wall.js?v=20260906m"></script>
 </body>
 </html>