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/assets/site.css

@@ -274,7 +274,9 @@ textarea{resize:vertical;font:inherit}
 .feat-day .fd-occ{font-family:var(--mono);font-size:11px;color:var(--muted)}
 .feat-day.open2 .fd-occ{color:var(--mint)}
 /* ── featured rotation strip ── */
-.feat-strip{display:flex;flex-direction:column;gap:8px;margin-top:10px}
+.feat-top{max-width:760px;margin:0 auto 16px}
+.feat-strip{display:flex;justify-content:center;margin-top:10px}
+.feat-strip a{max-width:728px;width:100%}
 .feat-strip a{display:flex;justify-content:space-between;gap:10px;padding:11px 14px;border-radius:10px;
   background:var(--panel);border:1px solid var(--line-strong);color:var(--ink);text-decoration:none;font-weight:600}
 .feat-strip a:hover{border-color:var(--mint)}