[Fonts] Retire max font size setting into theme CardText min/max range

The per-card text size lives in the theme now, so a theme can pick the size
it was designed for instead of every user overriding it globally.

- CardText stores family + max point size; CardTextMinSize stores the
  overlay shrink-to-fit floor (omitted from fonts.toml when 1).
- ThemeManager::cardTextMaxSize()/cardTextMinSize() resolve the range with
  the retired defaults (12 max, 1 min), and cardTextMaxSize() falls back to
  the CardText role size that #7541 made live.
- The overlay widget starts at the explicit size when one is set (deck
  preview), else the theme max, and shrinks down to the theme floor.
- The appearance page's "Maximum font size" spin is gone; the range is
  edited in the theme's font grid, whose min/max spins now keep the saved
  range consistent with each other.
- Migration: appearance/maxFontSize is seeded into every user theme folder
  and into the active theme's folder (created when the theme is a shipped
  one that only exists in the system directory). The retired
  game/maxfontsize -> appearance/maxFontSize mapping stays, so users still
  on global.ini keep their value through the chain.

cockatrice/src/interface/theme_config.h

@@ -128,15 +128,23 @@ struct PaletteConfig
  * @code
  * [Fonts]
  * InterfaceDefault = "Inter, 10"
+ * CardText = "Noto Serif, 12"
+ * CardTextMinSize = 1
  * @endcode
+ * CardText stores family + MAX size; cardTextMinSize stores the overlay
+ * shrink-to-fit floor (omitted from TOML when 1).
  */
 struct FontConfig
 {
     QMap<AppFont::Role, QFont> fonts;
+    int cardTextMinSize = 1;
+    /// Optional size-only maximum for CardText, used by the retired maxFontSize
+    /// migration so seeding it does not have to pin a family.
+    int cardTextMaxSize = 0;
 
     bool operator==(const FontConfig &rhs) const
     {
-        return fonts == rhs.fonts;
+        return fonts == rhs.fonts && cardTextMinSize == rhs.cardTextMinSize && cardTextMaxSize == rhs.cardTextMaxSize;
     }
     bool operator!=(const FontConfig &rhs) const
     {