**Refactor directory scanning and add scan task support**

- Added a new `scan_directory` task to enable folder scans as asynchronous tasks while maintaining compatibility with the immediate backend.
- Introduced the `reconcile` function, replacing `generate_directory` for improved separation of concerns between database writes and read operations.
- Established a unique constraint on `Directory` (`one_directory_name_per_parent`) to prevent duplicate directories under the same parent.
- Added a "Scan" button to the frontend for re-reading folders from disk, along with new task invocation endpoints in the API.
- Updated tests across modules to validate the new `scan_directory` task, unique constraints, and database indexing logic.
- Improved cleanup logic for stale files, directories, and thumbnails to handle concurrent operations efficiently.
- Simplified `scan_comics` management command by removing user dependency and aligning it with the new `reconcile` function.
- Enhanced frontend components (`TheComicReader`, `TheComicList`, and others) to include lifecycle method cleanups, prevent memory leaks, and handle task-based scans.

comic/tests/test_scan_command.py

@@ -23,9 +23,11 @@ def test_scan_indexes_nested_directories(comic_volume: Path, reader_user) -> Non
 
 
 @pytest.mark.django_db
-def test_scan_without_a_user_stops_before_reading_the_volume(comic_volume: Path) -> None:
+def test_scan_runs_without_any_user(comic_volume: Path) -> None:
+    """The command no longer needs a user, because statuses are created when a book is read."""
     make_cbz(comic_volume / 'issue.cbz', pages=1)
 
     call_command('scan_comics')
 
-    assert models.ComicBook.objects.count() == 0
+    assert models.ComicBook.objects.count() == 1
+    assert models.ComicStatus.objects.count() == 0