Admin: Letzte Aktivität pro User (nur echte Aktionen, kein Polling)

frontend/src/App.jsx

@@ -1499,6 +1499,22 @@ function UserManagement({ toast }) {
                   border:`1px solid ${u.role==='admin'?'rgba(255,230,109,0.3)':'rgba(78,205,196,0.3)'}`,
                   borderRadius:4, padding:'1px 6px',
                 }}>{u.role}</span>
+                {u.last_active_at && (
+                  <span style={{
+                    marginLeft:6, fontSize:9, fontFamily:'monospace',
+                    color:'rgba(255,255,255,0.35)',
+                  }}>
+                    ● {(() => {
+                      const d = new Date(u.last_active_at.replace(' ','T'));
+                      const now = new Date();
+                      const diff = Math.floor((now - d) / 60000);
+                      if (diff < 2)   return 'gerade eben';
+                      if (diff < 60)  return `vor ${diff} min`;
+                      if (diff < 1440) return `vor ${Math.floor(diff/60)} h`;
+                      return d.toLocaleDateString('de-DE', {day:'2-digit',month:'2-digit',hour:'2-digit',minute:'2-digit'});
+                    })()}
+                  </span>
+                )}
               </div>
               <div style={{display:'flex',gap:5}}>
                 <button onClick={()=>{setResetId(u.id);setResetPw('');}}