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/__tests__/FileManagerView.test.js

@@ -29,8 +29,8 @@ vi.mock('../../api/client.js', () => ({
 }))
 
 // Stub heavy child components so we only test FileManagerView logic
-vi.mock('../../components/folders/FolderBreadcrumb.vue', () => ({
-  default: { template: '<nav><slot/></nav>', props: ['segments'], emits: ['navigate'] },
+vi.mock('../../components/ui/BreadcrumbBar.vue', () => ({
+  default: { template: '<nav><slot/></nav>', props: ['segments', 'rootLabel', 'showRoot'], emits: ['navigate'] },
 }))
 vi.mock('../../components/upload/DropZone.vue', () => ({
   default: { template: '<div class="dropzone"/>', emits: ['files-selected'] },