feat(06.2-03): frontend — CloudDeleteWarningModal + remove_only path in DocumentView

- api/client.js: deleteDocument gains removeOnly param; deleteDocumentRemoveOnly wrapper added
- DocumentView.vue: confirmDelete inspects response.cloud_delete_failed, shows modal on failure
- DocumentView.vue: inline CloudDeleteWarningModal (C-3 contract) with Remove from app / Cancel
- confirmRemoveOnly() calls DELETE ?remove_only=true and navigates to /

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/views/DocumentView.vue

@@ -108,6 +108,40 @@
       :doc="doc"
       @close="showPreviewModal = false"
     />
+
+    <!-- Cloud delete warning modal -->
+    <div
+      v-if="showCloudDeleteWarning"
+      class="fixed inset-0 bg-black/40 flex items-center justify-center z-50"
+      @click.self="cancelCloudDeleteWarning"
+    >
+      <div
+        role="dialog"
+        aria-modal="true"
+        aria-labelledby="cloud-delete-modal-title"
+        class="bg-white rounded-2xl shadow-xl p-6 max-w-sm w-full mx-4"
+      >
+        <div class="flex items-center gap-2 mb-2">
+          <svg class="w-5 h-5 text-amber-500 shrink-0" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+            <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M12 9v2m0 4h.01m-6.938 4h13.856c1.54 0 2.502-1.667 1.732-3L13.732 4c-.77-1.333-2.694-1.333-3.464 0L3.34 16c-.77 1.333.192 3 1.732 3z" />
+          </svg>
+          <h2 id="cloud-delete-modal-title" class="text-lg font-semibold text-gray-900">Cloud delete failed</h2>
+        </div>
+        <p class="text-sm text-gray-600 mb-4">
+          The file could not be deleted from {{ cloudProviderName }}. Remove it from DocuVault anyway? The file will remain on {{ cloudProviderName }}.
+        </p>
+        <div class="flex gap-2 justify-end">
+          <button
+            @click="cancelCloudDeleteWarning"
+            class="border border-gray-300 text-gray-700 text-sm px-4 py-2 rounded-lg hover:bg-gray-50 transition-colors"
+          >Cancel</button>
+          <button
+            @click="confirmRemoveOnly"
+            class="bg-red-600 hover:bg-red-700 text-white text-sm px-4 py-2 rounded-lg transition-colors"
+          >Remove from app</button>
+        </div>
+      </div>
+    </div>
   </div>
 </template>
 
@@ -135,6 +169,8 @@ const suggestions = ref([])
 const selectedSuggestions = ref([])
 const showPreviewModal = ref(false)
 const pdfOpenMode = ref('new_tab')
+const showCloudDeleteWarning = ref(false)
+const cloudProviderName = ref('your cloud storage')
 
 const isPdf = computed(() => {
   if (!doc.value) return false
@@ -229,12 +265,33 @@ async function createSelectedTopics() {
   await reclassify()
 }
 
+const _PROVIDER_NAMES = { google_drive: 'Google Drive', onedrive: 'OneDrive', nextcloud: 'Nextcloud', webdav: 'WebDAV' }
+
 async function confirmDelete() {
   if (!confirm(`Delete "${doc.value.original_name}"?`)) return
-  await docsStore.remove(doc.value.id)
+  const resp = await api.deleteDocument(doc.value.id)
+  if (resp && resp.cloud_delete_failed) {
+    cloudProviderName.value = _PROVIDER_NAMES[doc.value.storage_backend] || 'your cloud storage'
+    showCloudDeleteWarning.value = true
+    return
+  }
   router.push('/')
 }
 
+async function confirmRemoveOnly() {
+  try {
+    await api.deleteDocumentRemoveOnly(doc.value.id)
+    showCloudDeleteWarning.value = false
+    router.push('/')
+  } catch (e) {
+    // error shown inline if needed — modal stays open
+  }
+}
+
+function cancelCloudDeleteWarning() {
+  showCloudDeleteWarning.value = false
+}
+
 function formatDate(iso) {
   if (!iso) return ''
   return new Date(iso).toLocaleDateString(undefined, { month: 'short', day: 'numeric', year: 'numeric' })