Lehrer: Default-Klasse = zuletzt gewählte (persistent), Fallback älteste

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

App/teacher.html

@@ -2004,7 +2004,17 @@ async function loadClasses() {
     opt.value = c.id; opt.textContent = c.name + ' (' + c.school_year + ')';
     sel.appendChild(opt);
   });
-  if (!currentClassId) currentClassId = classes[0].id;
+  // Default-Klasse: zuletzt gewählte (persistent gemerkt), sonst die ÄLTESTE.
+  if (!currentClassId) {
+    var saved = null;
+    try { saved = parseInt(localStorage.getItem('ggs-last-class'), 10); } catch(_) {}
+    if (saved && classes.some(function(c){ return c.id === saved; })) {
+      currentClassId = saved;
+    } else {
+      var byAge = classes.slice().sort(function(a,b){ return (a.created_at||'') < (b.created_at||'') ? -1 : 1; });
+      currentClassId = byAge[0].id;   // älteste zuerst
+    }
+  }
   sel.value = currentClassId;
   currentClass = classes.find(function(c) { return c.id === currentClassId; });
   document.getElementById('class-code').textContent = currentClass?.join_code || '—';
@@ -2025,6 +2035,7 @@ async function loadClasses() {
 
 function onClassChange() {
   currentClassId = parseInt(document.getElementById('class-select').value);
+  try { localStorage.setItem('ggs-last-class', currentClassId); } catch(_) {}   // „letzter Aufruf" merken
   currentClass = allClasses.find(function(c) { return c.id === currentClassId; });
   document.getElementById('class-code').textContent = currentClass?.join_code || '—';
   loadTab(currentTab);