perf(stability): add request metrics and resilient API retries

admin-frontend/src/layouts/AdminLayout.vue

@@ -34,7 +34,11 @@ async function refreshStats() {
 
 const loadingBadges = ref(false)
 const pendingFeedbackCount = ref(0)
-let badgeTimer
+
+const BADGE_POLL_ACTIVE_MS = 60_000
+const BADGE_POLL_HIDDEN_MS = 180_000
+
+let badgeTimer = null
 
 async function refreshNavBadges(partial = null) {
   if (partial && typeof partial === 'object') {
@@ -55,6 +59,34 @@ async function refreshNavBadges(partial = null) {
   }
 }
 
+function isPageHidden() {
+  if (typeof document === 'undefined') return false
+  return document.visibilityState === 'hidden'
+}
+
+function currentBadgePollDelay() {
+  return isPageHidden() ? BADGE_POLL_HIDDEN_MS : BADGE_POLL_ACTIVE_MS
+}
+
+function stopBadgePolling() {
+  if (!badgeTimer) return
+  window.clearTimeout(badgeTimer)
+  badgeTimer = null
+}
+
+function scheduleBadgePolling() {
+  stopBadgePolling()
+  badgeTimer = window.setTimeout(async () => {
+    badgeTimer = null
+    await refreshNavBadges().catch(() => {})
+    scheduleBadgePolling()
+  }, currentBadgePollDelay())
+}
+
+function onVisibilityChange() {
+  scheduleBadgePolling()
+}
+
 provide('refreshStats', refreshStats)
 provide('adminStats', stats)
 provide('refreshNavBadges', refreshNavBadges)
@@ -75,12 +107,14 @@ onMounted(async () => {
 
   await refreshStats()
   await refreshNavBadges()
-  badgeTimer = window.setInterval(refreshNavBadges, 60_000)
+  scheduleBadgePolling()
+  window.addEventListener('visibilitychange', onVisibilityChange)
 })
 
 onBeforeUnmount(() => {
   mediaQuery?.removeEventListener?.('change', syncIsMobile)
-  window.clearInterval(badgeTimer)
+  stopBadgePolling()
+  window.removeEventListener('visibilitychange', onVisibilityChange)
 })
 
 const menuItems = [