feat: Excel import/export module via SheetJS

js/excel.js

@@ -0,0 +1,35 @@
+// Reads employee names from first column of xlsx (skips header row 0)
+export function readEmployeeNames(arrayBuffer) {
+  const wb = XLSX.read(arrayBuffer, { type: 'array' });
+  const sheet = wb.Sheets[wb.SheetNames[0]];
+  const rows = XLSX.utils.sheet_to_json(sheet, { header: 1 });
+  return rows.slice(1)
+    .map(row => String(row[0] ?? '').trim())
+    .filter(name => name.length > 0);
+}
+
+// Exports schedule as xlsx blob
+// assignments: [{ date: "2026-04-01", employeeId }]
+// employees: [{ id, name }]
+export function exportSchedule(assignments, employees) {
+  const nameById = Object.fromEntries(employees.map(e => [e.id, e.name]));
+  const names = assignments.map(a => nameById[a.employeeId] ?? '');
+  const dates = assignments.map(a => {
+    const [y, m, d] = a.date.split('-');
+    return d + '.' + m + '.' + y;
+  });
+  const ws = XLSX.utils.aoa_to_sheet([names, dates]);
+  const wb = XLSX.utils.book_new();
+  XLSX.utils.book_append_sheet(wb, ws, 'Moderationsplan');
+  const buf = XLSX.write(wb, { type: 'array', bookType: 'xlsx' });
+  return new Blob([buf], { type: 'application/octet-stream' });
+}
+
+export function downloadBlob(blob, filename) {
+  const url = URL.createObjectURL(blob);
+  const a = document.createElement('a');
+  a.href = url;
+  a.download = filename;
+  a.click();
+  URL.revokeObjectURL(url);
+}