fix: ensure all NFO properties are written on creation

- Add showtitle and namedseason to mapper output
- Add multi-language fallback (en-US, ja-JP) for empty overview
- Use search result overview as last resort fallback
- Add tests for new NFO creation behavior

tests/unit/test_nfo_service.py

@@ -1385,3 +1385,152 @@ class TestYearExtractionComprehensive:
         assert clean_name == "Series (12345)"
         assert year is None
 
+
+class TestEnrichFallbackLanguages:
+    """Tests for multi-language fallback and search overview fallback."""
+
+    @pytest.mark.asyncio
+    async def test_japanese_fallback_when_english_also_empty(
+        self, nfo_service, tmp_path,
+    ):
+        """ja-JP fallback is tried when both de-DE and en-US are empty."""
+        series_folder = tmp_path / "Rare Anime"
+        series_folder.mkdir()
+
+        de_data = {
+            "id": 55555, "name": "Rare Anime",
+            "original_name": "レアアニメ", "first_air_date": "2024-01-01",
+            "overview": "",
+            "vote_average": 7.0, "vote_count": 50,
+            "status": "Continuing", "episode_run_time": [24],
+            "genres": [], "networks": [], "production_countries": [],
+            "poster_path": None, "backdrop_path": None,
+            "external_ids": {}, "credits": {"cast": []},
+            "images": {"logos": []},
+        }
+        en_data = {"id": 55555, "overview": ""}
+        ja_data = {"id": 55555, "overview": "日本語のあらすじ"}
+
+        async def side_effect(tv_id, **kwargs):
+            lang = kwargs.get("language")
+            if lang == "ja-JP":
+                return ja_data
+            if lang == "en-US":
+                return en_data
+            return de_data
+
+        with patch.object(nfo_service.tmdb_client, 'search_tv_show', new_callable=AsyncMock) as mock_search, \
+             patch.object(nfo_service.tmdb_client, 'get_tv_show_details', new_callable=AsyncMock) as mock_details, \
+             patch.object(nfo_service.tmdb_client, 'get_tv_show_content_ratings', new_callable=AsyncMock) as mock_ratings, \
+             patch.object(nfo_service, '_download_media_files', new_callable=AsyncMock):
+
+            mock_search.return_value = {
+                "results": [{"id": 55555, "name": "Rare Anime", "first_air_date": "2024-01-01"}],
+            }
+            mock_details.side_effect = side_effect
+            mock_ratings.return_value = {"results": []}
+
+            nfo_path = await nfo_service.create_tvshow_nfo(
+                "Rare Anime", "Rare Anime",
+                download_poster=False, download_logo=False, download_fanart=False,
+            )
+
+            content = nfo_path.read_text(encoding="utf-8")
+            assert "<plot>日本語のあらすじ</plot>" in content
+
+    @pytest.mark.asyncio
+    async def test_search_overview_fallback_when_all_languages_empty(
+        self, nfo_service, tmp_path,
+    ):
+        """Search result overview is used as last resort."""
+        series_folder = tmp_path / "Brand New Anime"
+        series_folder.mkdir()
+
+        empty_data = {
+            "id": 77777, "name": "Brand New Anime",
+            "original_name": "新しいアニメ", "first_air_date": "2025-01-01",
+            "overview": "",
+            "vote_average": 0, "vote_count": 0,
+            "status": "Continuing", "episode_run_time": [],
+            "genres": [], "networks": [], "production_countries": [],
+            "poster_path": None, "backdrop_path": None,
+            "external_ids": {}, "credits": {"cast": []},
+            "images": {"logos": []},
+        }
+
+        async def side_effect(tv_id, **kwargs):
+            return empty_data
+
+        with patch.object(nfo_service.tmdb_client, 'search_tv_show', new_callable=AsyncMock) as mock_search, \
+             patch.object(nfo_service.tmdb_client, 'get_tv_show_details', new_callable=AsyncMock) as mock_details, \
+             patch.object(nfo_service.tmdb_client, 'get_tv_show_content_ratings', new_callable=AsyncMock) as mock_ratings, \
+             patch.object(nfo_service, '_download_media_files', new_callable=AsyncMock):
+
+            # Search result DOES have an overview
+            mock_search.return_value = {
+                "results": [{
+                    "id": 77777,
+                    "name": "Brand New Anime",
+                    "first_air_date": "2025-01-01",
+                    "overview": "Search result overview text.",
+                }],
+            }
+            mock_details.side_effect = side_effect
+            mock_ratings.return_value = {"results": []}
+
+            nfo_path = await nfo_service.create_tvshow_nfo(
+                "Brand New Anime", "Brand New Anime",
+                download_poster=False, download_logo=False, download_fanart=False,
+            )
+
+            content = nfo_path.read_text(encoding="utf-8")
+            assert "<plot>Search result overview text.</plot>" in content
+
+    @pytest.mark.asyncio
+    async def test_no_japanese_fallback_when_english_succeeds(
+        self, nfo_service, tmp_path,
+    ):
+        """Stop after en-US if it provides the overview."""
+        series_folder = tmp_path / "Test Anime"
+        series_folder.mkdir()
+
+        de_data = {
+            "id": 88888, "name": "Test Anime",
+            "original_name": "テスト", "first_air_date": "2024-01-01",
+            "overview": "",
+            "vote_average": 7.0, "vote_count": 50,
+            "status": "Continuing", "episode_run_time": [24],
+            "genres": [], "networks": [], "production_countries": [],
+            "poster_path": None, "backdrop_path": None,
+            "external_ids": {}, "credits": {"cast": []},
+            "images": {"logos": []},
+        }
+        en_data = {"id": 88888, "overview": "English overview."}
+
+        async def side_effect(tv_id, **kwargs):
+            lang = kwargs.get("language")
+            if lang == "en-US":
+                return en_data
+            return de_data
+
+        with patch.object(nfo_service.tmdb_client, 'search_tv_show', new_callable=AsyncMock) as mock_search, \
+             patch.object(nfo_service.tmdb_client, 'get_tv_show_details', new_callable=AsyncMock) as mock_details, \
+             patch.object(nfo_service.tmdb_client, 'get_tv_show_content_ratings', new_callable=AsyncMock) as mock_ratings, \
+             patch.object(nfo_service, '_download_media_files', new_callable=AsyncMock):
+
+            mock_search.return_value = {
+                "results": [{"id": 88888, "name": "Test Anime", "first_air_date": "2024-01-01"}],
+            }
+            mock_details.side_effect = side_effect
+            mock_ratings.return_value = {"results": []}
+
+            nfo_path = await nfo_service.create_tvshow_nfo(
+                "Test Anime", "Test Anime",
+                download_poster=False, download_logo=False, download_fanart=False,
+            )
+
+            content = nfo_path.read_text(encoding="utf-8")
+            assert "<plot>English overview.</plot>" in content
+            # de-DE + en-US = 2 calls (no ja-JP needed)
+            assert mock_details.call_count == 2
+