feat: add admin components for input, metrics, tables, and user forms

- Introduced AdminInput component for standardized input fields.
- Created AdminMetricCard for displaying metrics with customizable tones.
- Added AdminPlaceholderTable for loading states in tables.
- Developed AdminSectionCard for consistent section layouts.
- Implemented AdminSectionShell for organizing admin sections.
- Added AdminSelect for dropdown selections with v-model support.
- Created AdminTable for displaying tabular data with loading and empty states.
- Introduced AdminTextarea for multi-line text input.
- Developed AdminUserFormFields for user creation and editing forms.
- Added useAdminPageHeader composable for managing admin page header state.

src/composables/useNetworkStatus.ts

@@ -0,0 +1,47 @@
+import { ref } from 'vue'
+
+const isOffline = ref(false)
+
+let listenersCount = 0
+
+function syncNetworkStatus() {
+  if (typeof navigator === 'undefined') return
+
+  isOffline.value = !navigator.onLine
+}
+
+function handleNetworkStatusChange() {
+  syncNetworkStatus()
+}
+
+function startListening() {
+  if (typeof window === 'undefined') return
+
+  if (listenersCount === 0) {
+    syncNetworkStatus()
+    window.addEventListener('online', handleNetworkStatusChange)
+    window.addEventListener('offline', handleNetworkStatusChange)
+  }
+
+  listenersCount += 1
+}
+
+function stopListening() {
+  if (typeof window === 'undefined' || listenersCount === 0) return
+
+  listenersCount -= 1
+
+  if (listenersCount === 0) {
+    window.removeEventListener('online', handleNetworkStatusChange)
+    window.removeEventListener('offline', handleNetworkStatusChange)
+  }
+}
+
+export function useNetworkStatus() {
+  return {
+    isOffline,
+    syncNetworkStatus,
+    startListening,
+    stopListening,
+  }
+}