feat(admin): migrate admin UI to Vue3

admin-frontend/src/utils/datetime.js

@@ -0,0 +1,17 @@
+export function parseSqliteDateTime(value) {
+  if (!value) return null
+  if (value instanceof Date) return value
+
+  const str = String(value)
+  // "YYYY-MM-DD HH:mm:ss" -> "YYYY-MM-DDTHH:mm:ss"
+  const iso = str.includes('T') ? str : str.replace(' ', 'T')
+  const date = new Date(iso)
+  if (Number.isNaN(date.getTime())) return null
+  return date
+}
+
+export function formatDateTime(value) {
+  if (!value) return '-'
+  return String(value)
+}
+