Paginate the live payment proof feed (Show more / Show fewer)

The feed showed only the latest 12 of 136 recorded payouts. Now:
- chain.getPayoutsPublic(offset,limit) returns a page of the full
  reversed history plus total/offset/limit/hasMore (limit capped 100).
- /api/public/payouts accepts ?offset & ?limit (defaults 0/40, so the
  live poll + toast detection are unchanged).
- payouts.js keeps a deduped store keyed by payout key; the live poll
  refreshes the recent page while "Show more" pulls older pages 12 at a
  time (with slight overlap so a newly-arrived payout can't open a gap),
  and "Show fewer" collapses back. Verified in-browser: 12 → 48 → 136
  rows, button flips to "Show fewer", collapses to 12, 0 console errors.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

server.js

@@ -368,7 +368,10 @@ async function handleApi(req,res,pathname){
     }catch(e){return json(res,502,{error:e.message||'Lookup failed'})}
   }
   if(req.method==='GET'&&pathname==='/api/public/payouts'){
-    return json(res,200,chain.getPayoutsPublic(),{'Cache-Control':'public, max-age=20'});
+    const q=new URL(req.url,'http://x').searchParams;
+    const offset=Number(q.get('offset')||0);
+    const limit=Number(q.get('limit')||40);
+    return json(res,200,chain.getPayoutsPublic(offset,limit),{'Cache-Control':'public, max-age=20'});
   }
   if(req.method==='GET'&&pathname==='/api/public/org-stats'){
     const root=Number(getConfig().orgRootId||21);