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

src/core/utils/nfo_mapper.py

@@ -14,6 +14,7 @@ from typing import Any, Callable, Dict, List, Optional
 from src.core.entities.nfo_models import (
     ActorInfo,
     ImageInfo,
+    NamedSeason,
     RatingInfo,
     TVShowNFO,
     UniqueID,
@@ -167,6 +168,17 @@ def tmdb_to_nfo_model(
             tmdbid=member["id"],
         ))
 
+    # --- Named seasons ---
+    named_seasons: List[NamedSeason] = []
+    for season_info in tmdb_data.get("seasons", []):
+        season_name = season_info.get("name")
+        season_number = season_info.get("season_number")
+        if season_name and season_number is not None:
+            named_seasons.append(NamedSeason(
+                number=season_number,
+                name=season_name,
+            ))
+
     # --- Unique IDs ---
     unique_ids: List[UniqueID] = []
     if tmdb_data.get("id"):
@@ -194,6 +206,7 @@ def tmdb_to_nfo_model(
     return TVShowNFO(
         title=title,
         originaltitle=original_title,
+        showtitle=title,
         sorttitle=title,
         year=year,
         plot=tmdb_data.get("overview") or None,
@@ -215,6 +228,7 @@ def tmdb_to_nfo_model(
         thumb=thumb_images,
         fanart=fanart_images,
         actors=actors,
+        namedseason=named_seasons,
         watched=False,
         dateadded=datetime.now().strftime("%Y-%m-%d %H:%M:%S"),
     )