feat(10-08): BreadcrumbBar in remaining admin views + SettingsView; EmptyState in SharedView + CloudStorageView

- AdminQuotasView: BreadcrumbBar (Quotas, showRoot=false)
- AdminAiView: BreadcrumbBar (AI Config, showRoot=false)
- AdminOverviewView: BreadcrumbBar (empty segments, showRoot=false) above existing h2
- SettingsView: BreadcrumbBar with breadcrumbSegments computed (Settings > activeTabLabel)
- SharedView: BreadcrumbBar (Shared with me) + EmptyState (icon=inbox)
- CloudStorageView: BreadcrumbBar in toolbar + EmptyState (icon=cloud) with Settings router-link CTA
- Full test suite: 178 passed, 0 failures

frontend/src/views/SettingsView.vue

@@ -1,5 +1,7 @@
 <template>
   <div class="p-8 max-w-3xl mx-auto">
+    <BreadcrumbBar :segments="breadcrumbSegments" :show-root="false" class="mb-4" />
+
     <h2 class="text-2xl font-semibold text-gray-900 mb-1">Settings</h2>
     <p class="text-sm text-gray-500 mb-6">Account-level options for your DocuVault workspace.</p>
 
@@ -84,12 +86,13 @@
 </template>
 
 <script setup>
-import { ref, onMounted } from 'vue'
+import { ref, computed, onMounted } from 'vue'
 import { useRouter } from 'vue-router'
 import SettingsPreferencesTab from '../components/settings/SettingsPreferencesTab.vue'
 import SettingsAiTab from '../components/settings/SettingsAiTab.vue'
 import SettingsCloudTab from '../components/settings/SettingsCloudTab.vue'
 import SettingsAccountTab from '../components/settings/SettingsAccountTab.vue'
+import BreadcrumbBar from '../components/ui/BreadcrumbBar.vue'
 
 const router = useRouter()
 
@@ -101,6 +104,11 @@ const tabs = [
 ]
 
 const activeTab = ref('preferences')
+
+const breadcrumbSegments = computed(() => {
+  const tab = tabs.find(t => t.id === activeTab.value)
+  return [{ label: 'Settings' }, { label: tab?.label ?? activeTab.value }]
+})
 const oauthSuccessProvider = ref(null)
 const oauthError = ref(null)