[VisualDatabase] Draw the card grid with a model/view (#7701)

* [VisualDatabase] Draw the card grid with a model/view instead of a widget per card

The visual card database built one CardInfoPictureWithTextOverlayWidget per
card, 100 per page, and tore them down on every search, resize and scroll
page. It also looked each card up again by name from the model row, kept a
shadow QList<ExactCard>, and carried paging state plus a 5 s timer that only
existed to defer the first page.

Replace that with a real view on a flattened model:

- CardDatabaseDisplayModel gains CardInfoRole and cardInfoAt(), so a view can
  get the CardInfoPtr behind a proxy row without a name round trip.
- New CardDatabaseVisualDisplayModel (libcockatrice_models) flattens the
  filtered and sorted proxy into one entry per displayed card picture: the
  preferred printing normally, every printing of the selected sets while set
  filters are active. Proxy changes rebuild it on a 30 ms coalescing timer.
- New CardDatabaseVisualView (QListView IconMode) paints only visible rows
  through the new CardPictureDelegate, keeps the old interaction contract
  (left/right/middle press -> cardClicked, hover -> cardHovered, Ctrl+wheel
  resize, no selection, no focus stealing, scroll to top on a new result) and
  repaints when CardPictureLoader reports an async image.
- CardSizeWidget::enableCtrlScrollResize() also watches scroll-area viewports,
  which is what makes Ctrl+wheel work over a QListView.
- VisualDatabaseDisplayWidget drops the paging, the shadow list, the dead
  members and the 5 s timer.

Behaviour-preserving: no gameplay change, no new user-facing strings.

* [VisualDatabase] Fix the card grid wheel step

QListView hands the delegate's item height to the scroll bar as its single step under ScrollPerPixel, so QAbstractSlider moved wheelScrollLines() whole card rows per notch. Handle the wheel in the view instead: one line is an eighth of the grid cell, so a notch moves about a third of a card row at any card size and still follows the OS line count.

---------

Co-authored-by: Lukas Brübach <Bruebach.Lukas@bdosecurity.de>

cockatrice/src/interface/card_picture_loader/card_picture_loader.cpp

@@ -238,6 +238,7 @@ void CardPictureLoader::imageLoaded(const ExactCard &card, const QImage &image)
     });
 
     card.emitPixmapUpdated();
+    emit getInstance().pixmapLoaded(card);
 }
 
 void CardPictureLoader::deleteAllLocalOverrides(const ExactCard &card)

cockatrice/src/interface/card_picture_loader/card_picture_loader.h

@@ -146,6 +146,14 @@ signals:
     /** @brief Emitted after the worker has finished clearing the network and redirect caches. */
     void networkCacheCleared();
 
+    /**
+     * @brief Emitted once an image has been loaded and put into the pixmap cache.
+     *
+     * Views that paint cards from the loader without owning a widget per card can
+     * listen to this to repaint the rows whose picture just became available.
+     */
+    void pixmapLoaded(const ExactCard &card);
+
 private slots:
     /**
      * @brief Triggered when the user changes the picture download settings.