Wire restore into the backup watcher and fix backup timestamps

The api queued .restore-requested but nothing consumed it, so restores silently did nothing. The watcher now services the restore sentinel by running restore.sh, and its instance_data mount is read-write so restore can lay files back down (the manual one-shot stays read-only). Backup stamps use a colon-free UTC form that Date could not parse, so the UI showed raw strings; normalize them before formatting.

frontend/src/views/settings/ShopdbBackupsList.vue

@@ -190,7 +190,7 @@
     <div v-if="restoreTarget" class="modal-backdrop" @click.self="closeRestore">
       <div class="modal">
         <h3>Restore this backup?</h3>
-        <p class="modal-set">{{ restoreTarget.snapshotid }}</p>
+        <p class="modal-set">{{ formatTaken(restoreTarget.takenat || restoreTarget.snapshotid) }}</p>
 
         <div class="compat" :class="restoreTarget.iscompatible ? 'ok' : 'warn'">
           <component :is="restoreTarget.iscompatible ? ShieldCheck : AlertTriangle" :size="18" />
@@ -356,7 +356,7 @@ const STALE_HOURS = 48
 
 const hoursSinceLastGood = computed(() => {
   if (!lastGoodAt.value) return null
-  const then = new Date(lastGoodAt.value.replace(/Z$/, 'Z')).getTime()
+  const then = new Date(normalizeStamp(lastGoodAt.value)).getTime()
   return (Date.now() - then) / 36e5
 })
 
@@ -383,11 +383,21 @@ const bannerSub = computed(() => {
 // -- Formatting -------------------------------------------------------------
 function formatTaken(value) {
   if (!value) return 'unknown'
-  const date = new Date(value.replace(/Z$/, 'Z'))
+  const date = new Date(normalizeStamp(value))
   if (Number.isNaN(date.getTime())) return value
   return date.toLocaleString()
 }
 
+// Backup ids and manifest stamps use a filename-safe UTC form with no colons
+// (YYYY-MM-DDTHHMMSSZ, sometimes prefixed with a site name), which the Date
+// parser rejects. Reinsert the colons so it parses as real ISO 8601.
+function normalizeStamp(value) {
+  const match = String(value).match(/(\d{4}-\d{2}-\d{2})T(\d{2})(\d{2})(\d{2})Z$/)
+  if (!match) return value
+  const [, day, hour, minute, second] = match
+  return `${day}T${hour}:${minute}:${second}Z`
+}
+
 function formatSize(bytes) {
   if (!bytes) return '0 B'
   const units = ['B', 'KB', 'MB', 'GB', 'TB']