feat(library): hide games from lists and stats

readme.md

@@ -31,6 +31,10 @@ To Be Played is split into three repositories:
   games closest to 100 %.
 - **Playtime history**: one row per game and day, for the activity view and the "most played in the last two weeks"
   dashboard banner.
+- **Hide games**: a user can hide a Steam game (e.g. a playtest or a tool). It leaves every list and number: library,
+  picker, Pile of Shame, activity, achievement summary, public profile and landing page stats. The sync still
+  updates its playtime, but no achievements, time to beat, moods or speedrun data are fetched for it. The library
+  lists hidden games with `hidden=true`.
 - **Wishlist**: synced from Steam with store price and discount.
 - **Broken image repair**: the frontend reports a Steam cover or achievement icon that does not load. At 01:30
   (Europe/Berlin) a job checks up to 200 reports. A cover that loads again is left alone; else the store's hashed
@@ -61,6 +65,7 @@ accepted only by `GET /api/public/profiles/library` in the `X-Profile-Ticket` he
 | `GET` | `/api/library/games`, `/api/library/games/{appid}` | JWT |
 | `PUT` | `/api/library/games/{appid}/backlog` | JWT |
 | `PUT` | `/api/library/games/{appid}/status` (status only, keeps rating, notes, priority) | JWT |
+| `PUT` | `/api/library/games/{appid}/hidden` (`{hidden}`; `409 MANUAL_GAME` for a game added by hand) | JWT |
 | `POST` | `/api/library/sync` | JWT |
 | `POST` | `/api/library/broken-images` (`{appid, kind}`, kind `COVER` or `ACHIEVEMENT_ICONS`; `204`) | JWT |
 | `GET` | `/api/library/picker?maxMinutes=&mood=&count=&exclude=` | JWT |
@@ -143,7 +148,7 @@ Inside a module: `api` (controllers, DTOs), `service` (business logic), `domain`
    the playtime growth of the day to `user_game_playtime_day`, and soft-deletes Steam games the user no longer
    owns. When Steam returns no games, the library stays as it is.
 5. `TimeToBeatService` and `MoodService` ask IGDB for missing or old time-to-beat and mood data, for Steam games
-   and manual games.
+   and manual games. Hidden games only get their playtime updated.
 6. After the commit, `LibrarySyncedEvent` starts `AchievementSyncService` and `SpeedrunService` (backlog games only)
    in the background.