feat(phase-4-09): wire components into views — sidebar, cards, home, folder, shared, settings, admin

- AppSidebar: add 'Shared with me' entry (purple icon, count badge) and Folders section with New folder CTA
- DocumentCard: add group class, hover-reveal share button, ShareModal v-if, shared indicator pill
- HomeView: add SearchBar + SortControls above document list; fetchFolders on mount
- FolderView: new view with FolderBreadcrumb, FolderRow list, inline new-subfolder input, document list
- SharedView: new view fetching /api/shares/received with owner_handle display and empty state
- DocumentView: add PDF preview logic (in_app=DocumentPreviewModal, new_tab=window.open); load preferences on mount
- SettingsView: add Document Preferences card with pdf_open_mode radio buttons, auto-save on change
- AdminView: add Audit Log tab alongside Users/Quotas/AI Config tabs

frontend/src/components/layout/AppSidebar.vue

@@ -32,6 +32,70 @@
         All Topics
       </router-link>
 
+      <!-- Shared with me entry -->
+      <router-link
+        to="/shared"
+        class="nav-link"
+        :class="{ 'nav-link-active': $route.path === '/shared' }"
+      >
+        <div class="w-4 h-4 mr-2 shrink-0 rounded bg-purple-50 flex items-center justify-center">
+          <svg class="w-3 h-3 text-purple-500" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+            <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2"
+              d="M20 13V6a2 2 0 00-2-2H6a2 2 0 00-2 2v7m16 0v5a2 2 0 01-2 2H6a2 2 0 01-2-2v-5m16 0h-2.586a1 1 0 00-.707.293l-2.414 2.414a1 1 0 01-.707.293h-3.172a1 1 0 01-.707-.293l-2.414-2.414A1 1 0 006.586 13H4" />
+          </svg>
+        </div>
+        <span class="flex-1">Shared with me</span>
+        <span
+          v-if="sharedCount > 0"
+          class="ml-auto bg-purple-100 text-purple-600 text-xs font-semibold rounded-full px-2 min-w-[18px] text-center"
+        >
+          {{ sharedCount }}
+        </span>
+      </router-link>
+
+      <!-- Folders section -->
+      <div class="mt-3">
+        <div class="flex items-center justify-between px-3 mb-1">
+          <p class="text-xs font-semibold text-gray-400 uppercase tracking-wider">Folders</p>
+          <button
+            @click="startNewFolder"
+            class="text-xs text-indigo-600 hover:underline"
+          >
+            New folder
+          </button>
+        </div>
+
+        <!-- New folder inline input -->
+        <div v-if="showNewFolderInput" class="px-3 mb-2">
+          <input
+            v-model="newFolderName"
+            type="text"
+            placeholder="Folder name"
+            class="block w-full border border-gray-300 rounded-lg px-2 py-1 text-xs focus:outline-none focus:ring-2 focus:ring-indigo-500"
+            @keydown.enter="submitNewFolder"
+            @keydown.escape="cancelNewFolder"
+            autofocus
+          />
+          <p v-if="newFolderError" class="text-red-500 text-xs mt-1">{{ newFolderError }}</p>
+        </div>
+
+        <!-- Folder list -->
+        <div v-if="foldersStore.loading && foldersStore.folders.length === 0" class="px-3 py-1 text-xs text-gray-400">Loading…</div>
+        <router-link
+          v-for="folder in foldersStore.folders"
+          :key="folder.id"
+          :to="`/folders/${folder.id}`"
+          class="nav-link text-sm"
+          :class="{ 'nav-link-active': $route.params.folderId === folder.id || $route.params.folderId === String(folder.id) }"
+        >
+          <svg class="w-4 h-4 mr-2 shrink-0 text-gray-400" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+            <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2"
+              d="M3 7a2 2 0 012-2h4l2 2h8a2 2 0 012 2v9a2 2 0 01-2 2H5a2 2 0 01-2-2V7z" />
+          </svg>
+          <span class="truncate flex-1">{{ folder.name }}</span>
+        </router-link>
+      </div>
+
       <!-- Topics list -->
       <div class="mt-3">
         <p class="px-3 text-xs font-semibold text-gray-400 uppercase tracking-wider mb-1">Topics</p>
@@ -108,19 +172,66 @@
 </template>
 
 <script setup>
-import { useRouter } from 'vue-router'
+import { ref, onMounted } from 'vue'
+import { useRouter, useRoute } from 'vue-router'
 import { useTopicsStore } from '../../stores/topics.js'
 import { useAuthStore } from '../../stores/auth.js'
+import { useFoldersStore } from '../../stores/folders.js'
 import QuotaBar from './QuotaBar.vue'
+import * as api from '../../api/client.js'
 
 const topicsStore = useTopicsStore()
 const authStore = useAuthStore()
+const foldersStore = useFoldersStore()
 const router = useRouter()
+const route = useRoute()
+
+const sharedCount = ref(0)
+const showNewFolderInput = ref(false)
+const newFolderName = ref('')
+const newFolderError = ref('')
+
+onMounted(async () => {
+  await foldersStore.fetchFolders(null)
+  try {
+    const data = await api.getSharedWithMe()
+    const items = Array.isArray(data) ? data : (data.items ?? [])
+    sharedCount.value = items.length
+  } catch {
+    sharedCount.value = 0
+  }
+})
 
 async function signOut() {
   await authStore.logout()
   router.push('/login')
 }
+
+function startNewFolder() {
+  newFolderName.value = ''
+  newFolderError.value = ''
+  showNewFolderInput.value = true
+}
+
+function cancelNewFolder() {
+  showNewFolderInput.value = false
+  newFolderError.value = ''
+}
+
+async function submitNewFolder() {
+  const trimmed = newFolderName.value.trim()
+  if (!trimmed) {
+    newFolderError.value = 'Folder name cannot be empty.'
+    return
+  }
+  try {
+    await foldersStore.createFolder(trimmed, null)
+    showNewFolderInput.value = false
+    newFolderError.value = ''
+  } catch (e) {
+    newFolderError.value = e.message || 'Failed to create folder.'
+  }
+}
 </script>
 
 <style scoped>