fix(recipes): make batch-import directory browser work on Windows (#1106)

The browse endpoint and its frontend were written with POSIX-only
assumptions, so on Windows pressing Browse immediately failed with
"Access denied to this directory":

- The frontend opened the browser at "/", which resolves to the
  current drive root on Windows.
- The allowlist check used Path("/"), which has no drive letter on
  Windows, so relative_to() rejected every drive-qualified path —
  anything outside the user profile was denied.

Fixes:
- Empty browse path now defaults to the user home directory instead of
  erroring; the frontend sends "" rather than the POSIX-only "/".
- The access check is platform-aware (drive-qualified on Windows,
  absolute on POSIX).
- Parent navigation uses the server-provided parent_path; the root
  check is now path.parent == path (the old str/anchor comparison
  self-looped at Windows drive roots).
- Browsing up from a Windows drive root shows a virtual list of
  available drives so users can switch drives without typing a path.

tests/frontend/managers/BatchImportManager.directoryBrowser.test.js

@@ -0,0 +1,112 @@
+import { describe, it, expect, beforeEach, afterEach, vi } from 'vitest';
+import { renderTemplate } from '../utils/domFixtures.js';
+
+vi.mock('../../../static/js/utils/uiHelpers.js', () => ({
+  showToast: vi.fn(),
+  setupAutoNewlineOnPaste: vi.fn(),
+}));
+
+vi.mock('../../../static/js/utils/i18nHelpers.js', () => ({
+  translate: (key, params = {}, fallback = null) => fallback ?? key,
+}));
+
+vi.mock('../../../static/js/api/apiConfig.js', () => ({
+  WS_ENDPOINTS: {},
+}));
+
+vi.mock('../../../static/js/utils/storageHelpers.js', () => ({
+  getStorageItem: vi.fn(() => true),
+  setStorageItem: vi.fn(),
+}));
+
+describe('BatchImportManager directory browser (#1106)', () => {
+  let batchImportManager;
+  let fetchMock;
+  let showToast;
+
+  beforeEach(async () => {
+    vi.clearAllMocks();
+    vi.resetModules();
+
+    document.body.innerHTML = '';
+    renderTemplate('components/batch_import_modal.html');
+
+    fetchMock = vi.fn(async () => ({
+      ok: true,
+      status: 200,
+      json: async () => ({ success: true }),
+    }));
+    vi.stubGlobal('fetch', fetchMock);
+
+    const uiHelpers = await import('../../../static/js/utils/uiHelpers.js');
+    showToast = uiHelpers.showToast;
+
+    const batchModule = await import('../../../static/js/managers/BatchImportManager.js');
+    batchImportManager = new batchModule.BatchImportManager();
+  });
+
+  afterEach(() => {
+    vi.unstubAllGlobals();
+  });
+
+  function lastRequestBody() {
+    return JSON.parse(fetchMock.mock.calls.at(-1)[1].body);
+  }
+
+  it('opens the browser with an empty path so the server picks the default', async () => {
+    // The old POSIX-only "/" initial path fails the access check on Windows.
+    document.getElementById('batchDirectoryInput').value = '';
+
+    batchImportManager.toggleDirectoryBrowser();
+
+    await vi.waitFor(() => expect(fetchMock).toHaveBeenCalled());
+    expect(lastRequestBody().path).toBe('');
+    expect(document.getElementById('batchDirectoryBrowser').style.display).toBe('block');
+  });
+
+  it('navigates to the parent using the server-provided path (Windows-safe)', async () => {
+    fetchMock.mockImplementation(async () => ({
+      ok: true,
+      status: 200,
+      json: async () => ({
+        success: true,
+        current_path: 'C:\\Users\\miao\\Pictures',
+        parent_path: 'C:\\Users\\miao',
+        directories: [],
+        image_files: [],
+        image_count: 0,
+        directory_count: 0,
+      }),
+    }));
+
+    await batchImportManager.loadDirectory('C:\\Users\\miao\\Pictures');
+    fetchMock.mockClear();
+
+    batchImportManager.navigateToParentDirectory();
+
+    await vi.waitFor(() => expect(fetchMock).toHaveBeenCalled());
+    expect(lastRequestBody().path).toBe('C:\\Users\\miao');
+  });
+
+  it('refuses to select a virtual level that has no current path (drive list)', async () => {
+    fetchMock.mockImplementation(async () => ({
+      ok: true,
+      status: 200,
+      json: async () => ({
+        success: true,
+        current_path: '',
+        parent_path: null,
+        directories: [{ name: 'C:\\', path: 'C:\\', is_parent: false }],
+        image_files: [],
+        image_count: 0,
+        directory_count: 1,
+      }),
+    }));
+
+    await batchImportManager.loadDirectory('__drives__');
+    batchImportManager.selectCurrentDirectory();
+
+    expect(showToast).toHaveBeenCalledWith('toast.recipes.batchImportNoDirectory', {}, 'error');
+    expect(document.getElementById('batchDirectoryInput').value).toBe('');
+  });
+});