Save source descriptions, add "Why it's #N", fix IGDB studio names

Descriptions
- Items keep the source's description (TMDB/TheTVDB overview, IGDB
  summary, Wikipedia intro) in a new items.description column
  (migration 3); editable in the item form
- Deezer/MusicBrainz track counts and album names are now display-only
  hints, not saved as descriptions

Why it's #N
- The owner's note is presented as "Why it's #N" in the editor and the
  public detail view, above an "About" section with the description

IGDB developers
- IGDB credits internal divisions ("Nintendo EAD", "Nintendo EPD
  Production Group No. 8"). A developer whose name shares its first word
  with its parent company is credited to the parent ("Nintendo");
  independently named studios keep their name (Retro Studios, Naughty
  Dog, Landfall Games)
- Fall back to the publisher when IGDB lists no developer

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -13,7 +13,7 @@ Visitors just see your lists. There's no sign-up, no feed and no login button. Y
 - **Drag to rank**, or use the arrow buttons or type a new number. Paginated editing keeps huge lists usable.
 - **Art is cached on your server**, so pages never hotlink and keep working if a source changes. You can also paste an image URL or upload your own.
 - **Export** any list as a titles-only `.csv` or `.txt`.
-- **Personal notes** on any entry, shown in a detail view (toggleable).
+- **Descriptions and your reasons**: each entry keeps the source's description (TMDB overview, IGDB summary, Wikipedia intro), and you can add a "Why it's #N" note explaining its spot. Both show in the detail view.
 - **12 theme presets** plus a custom CSS box. Every color is a CSS variable.
 - **Single binary + SQLite**, no external database. Around 15 MB, and it runs anywhere Docker does.