Earn-and-spend credit economy + private rehearsal chain cutover

Members earn credits by attention (spec 8b): daily 5-ad set with dwell
timing and a too-fast guard, then a claimable daily batch. Earned credits
now FUND campaigns: banner/text budgets draw earned-first (free members can
advertise on welcome credits alone), purchased credits and the on-chain
burn queue only cover the remainder; earned-only campaigns pause when the
pool runs dry. New Earn credits section in the member menu with the viewer.
Explorer links degrade gracefully for the private chain (contract page
points at the audited Amoy verification). Site flipped to the anvil
rehearsal chain at rpc.instantadpay.com: unlimited test POL, no more
faucets. E2E: welcome->views->claim->earned-funded campaign->charged
serving, all green. Assets v=20260905d.

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

public/assets/common.js

@@ -85,7 +85,9 @@ window.IAP = (function () {
     const div = document.createElement('div');
     div.className = 'row t-' + ev.type;
     div.innerHTML = '<span>' + describeEvent(ev, c) + '</span>'
-      + '<span class="tx"><a target="_blank" rel="noopener" href="' + c.explorer + '/tx/' + ev.tx + '">verify ↗</a></span>';
+      + (c.explorer
+        ? '<span class="tx"><a target="_blank" rel="noopener" href="' + c.explorer + '/tx/' + ev.tx + '">verify ↗</a></span>'
+        : '<span class="tx mono">' + ev.tx.slice(0, 12) + '…</span>');
     return div;
   }
   // Render one served ad into #<elId>. Silent if no inventory.