feat(10-06): wire breadcrumb mapping + toast call sites; delete FolderBreadcrumb

- FileManagerView: add mappedBreadcrumb computed ({id,label} from foldersStore.breadcrumb)
- FileManagerView: import useToastStore; add toast.show() to doMove, doDeleteDoc, onFilesSelected
- FileManagerView: remove console.error from doMove/doDeleteDoc (toast communicates errors)
- CloudFolderView: add mappedBreadcrumb computed; pass to StorageBrowser :breadcrumb
- Delete FolderBreadcrumb.vue + FolderBreadcrumb.test.js (no dead code per CLAUDE.md)
- FileManagerView.test.js: replace dead FolderBreadcrumb mock with BreadcrumbBar mock
- StorageBrowser.skeleton.test.js: remove unused FolderBreadcrumb stub
- Full suite: 164/164 pass, 0 failures

frontend/src/views/CloudFolderView.vue

@@ -3,7 +3,7 @@
     mode="cloud"
     :folders="folders"
     :files="files"
-    :breadcrumb="breadcrumb"
+    :breadcrumb="mappedBreadcrumb"
     :upload-queue="uploadQueue"
     :loading="loading"
     :empty-message="error || 'This folder is empty'"
@@ -45,6 +45,10 @@ const breadcrumb = computed(() => {
   }))
 })
 
+const mappedBreadcrumb = computed(() =>
+  breadcrumb.value.map(f => ({ id: f.id, label: f.name }))
+)
+
 async function load() {
   loading.value = true
   error.value = ''