[Fonts] Keep CardText call sites on the app font and fix px sizes

- CardText's unset fallback is qApp->font() again: only the three counter
  painters (paintNumberEllipse, GeneralCounter, PlayerCounter) were Serif
  before the role existed, and they now ask for it through
  ThemeManager::cardTextFont(). Card names, player names, counters, the
  overlay, the Archidekt and EDHREC labels and the completer delegate keep the
  app font they used before.
- Use setPixelSize for the EDHREC card name (20px) and commander name (28px)
  and details (16px) sizes: the stylesheets said px, and setPointSize made
  them about a third larger.

cockatrice/src/interface/theme_manager.cpp

@@ -666,12 +666,9 @@ QFont ThemeManager::appFont(AppFont::Role role) const
         // (report_utils::reportLogFont) instead of through this fallback.
         return qApp->font();
     }
-    if (role == AppFont::CardText) {
-        return QFont(QStringLiteral("Serif"));
-    }
-
-    // No per-role scaling: every other unset role resolves to the application
-    // font, so with no fonts.toml present the result is identical to before.
+    // No per-role scaling: an unset role resolves to the application font, so
+    // with no fonts.toml present the result is identical to before. The counter
+    // painters that used to hardcode Serif ask for it through cardTextFont().
     return qApp->font();
 }
 
@@ -680,6 +677,16 @@ bool ThemeManager::hasAppFont(AppFont::Role role) const
     return currentFonts.fonts.contains(role);
 }
 
+QFont ThemeManager::cardTextFont() const
+{
+    if (hasAppFont(AppFont::CardText)) {
+        return appFont(AppFont::CardText);
+    }
+    QFont serifFont(QStringLiteral("Serif"));
+    serifFont.setStyleHint(QFont::Serif);
+    return serifFont;
+}
+
 QFont ThemeManager::defaultAppFont(AppFont::Role /*role*/) const
 {
     // No per-role scaling and no preview: an unset role resolves to the font