feat: write all required NFO tags on creation

docs/NFO_GUIDE.md

@@ -636,7 +636,44 @@ curl -X POST "http://127.0.0.1:8000/api/scheduler/config" \
 
 ---
 
-## 10. Support
+## 10. Tag Reference
+
+The table below lists every XML tag written to `tvshow.nfo` and its source in
+the TMDB API response.  All tags are written whenever the NFO is created or
+updated via `create_tvshow_nfo()` / `update_tvshow_nfo()`.
+
+| NFO tag         | TMDB source field                              | Required |
+| --------------- | ---------------------------------------------- | -------- |
+| `title`         | `name`                                         | ✅        |
+| `originaltitle` | `original_name`                                | ✅        |
+| `showtitle`     | `name` (same as `title`)                       | ✅        |
+| `sorttitle`     | `name` (same as `title`)                       | ✅        |
+| `year`          | First 4 chars of `first_air_date`              | ✅        |
+| `plot`          | `overview`                                     | ✅        |
+| `outline`       | `overview` (same as `plot`)                    | ✅        |
+| `tagline`       | `tagline`                                      | optional |
+| `runtime`       | `episode_run_time[0]`                          | ✅        |
+| `premiered`     | `first_air_date`                               | ✅        |
+| `status`        | `status`                                       | ✅        |
+| `mpaa`          | US content rating from `content_ratings.results`| optional |
+| `fsk`           | DE content rating (written as `mpaa` when preferred) | optional |
+| `imdbid`        | `external_ids.imdb_id`                         | ✅        |
+| `tmdbid`        | `id`                                           | ✅        |
+| `tvdbid`        | `external_ids.tvdb_id`                         | optional |
+| `genre`         | `genres[].name` (one element per genre)        | ✅        |
+| `studio`        | `networks[].name` (one element per network)    | ✅        |
+| `country`       | `origin_country[]` or `production_countries[].name` | ✅  |
+| `actor`         | `credits.cast[]` (top 10, with name/role/thumb)| ✅        |
+| `watched`       | Always `false` on creation                     | ✅        |
+| `dateadded`     | System clock at creation time (`YYYY-MM-DD HH:MM:SS`) | ✅  |
+
+The mapping logic lives in `src/core/utils/nfo_mapper.py` (`tmdb_to_nfo_model`).
+The XML serialisation lives in `src/core/utils/nfo_generator.py`
+(`generate_tvshow_nfo`).
+
+---
+
+## 11. Support
 
 ### Getting Help