Add Step 4 fallback: generate key from folder name

- SerieScanner: generate key from folder when no key/data files exist
- Handle edge cases: non-Latin characters, special symbols in folder names
- anime_service: expose loading_status and loading_error fields
- Update tests to match new fallback behavior

src/server/services/anime_service.py

@@ -528,6 +528,8 @@ class AnimeService:
                         "tmdb_id": db_series.tmdb_id,
                         "tvdb_id": db_series.tvdb_id,
                         "series_id": db_series.id,
+                        "loading_status": db_series.loading_status,
+                        "loading_error": db_series.loading_error,
                     }
                     
                     # Build episodeDict from DB, skipping is_downloaded=True
@@ -596,6 +598,8 @@ class AnimeService:
                     "tmdb_id": nfo_data.get("tmdb_id"),
                     "tvdb_id": nfo_data.get("tvdb_id"),
                     "series_id": nfo_data.get("series_id"),
+                    "loading_status": nfo_data.get("loading_status"),
+                    "loading_error": nfo_data.get("loading_error"),
                 }
                 result_list.append(series_dict)