Announcement card: a notice can explain itself

The cancellation card could only say two lines, an eyebrow and a date label,
because the card has no prose field and the API never passed one. A notice needs
to say what happened and what comes next, so it now carries a body.

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

public/announce.js

@@ -71,6 +71,14 @@
         foot.appendChild(dateRow);
       }
 
+      // a notice (cancellation, change of plan) carries prose where an invitation carries times
+      if (EV.body) {
+        var bodyEl = document.createElement('p');
+        bodyEl.textContent = EV.body;
+        bodyEl.style.cssText = 'margin:10px 0 2px;text-align:center;color:#c8d6e2;font-size:14.5px;line-height:1.5;';
+        foot.appendChild(bodyEl);
+      }
+
       if (EV.timesArr.length) {
         var grid = document.createElement('div');
         grid.style.cssText = 'display:grid;grid-template-columns:1fr 1fr;gap:8px;margin-bottom:16px;';