Add web app install button and step-by-step PWA guide.

src/App.vue

@@ -85,6 +85,12 @@
   />
 
   <VersionUpdateModal />
+
+  <PwaInstallGuideModal
+    v-model:open="guideOpen"
+    :platform="platform"
+    @complete="completeGuide()"
+  />
 </template>
 
 <script lang="ts" setup>
@@ -102,6 +108,8 @@ import AppCreditLink from '@/components/AppCreditLink.vue'
 import SupportMessengerPicker from '@/components/SupportMessengerPicker.vue'
 import { useRoute } from 'vue-router'
 import { recoverMobileViewportAfterAuth } from '@/layouts/composables/useMobileScrollReset'
+import { usePwaInstall } from '@/composables/usePwaInstall'
+import PwaInstallGuideModal from '@/components/pwa/PwaInstallGuideModal.vue'
 
 const VersionUpdateModal = defineAsyncComponent(
   () => import('@/modules/version/VersionUpdateModal.vue')
@@ -120,6 +128,12 @@ const config = useConfigStore()
 const showSplash = ref(true)
 const popVisible = ref(false)
 
+const {
+  guideOpen,
+  platform,
+  completeGuide,
+} = usePwaInstall()
+
 const {
   supportPickerOpen,
   supportPickerAnchor,