Scale preview padding in UITheme metrics

Apply scaling to previewPadding metric while keeping previewHeightPercent intentionally unscaled. Adds clarifying comment about the different scaling behavior between these two preview-related metrics.

src/components/UITheme.cpp

@@ -40,6 +40,9 @@ ThemeMetrics scaleThemeMetrics(const ThemeMetrics& b, float s) {
   m.batteryBarHeight = sp(b.batteryBarHeight, s);
   m.headerHeight = sp(b.headerHeight, s);
   m.verticalSpacing = sp(b.verticalSpacing, s);
+  // previewPadding is a pixel inset (font preview pane); scaled. previewHeightPercent is a
+  // percent of the usable height and is intentionally NOT scaled.
+  m.previewPadding = sp(b.previewPadding, s);
   m.contentSidePadding = sp(b.contentSidePadding, s);
   m.listRowHeight = sp(b.listRowHeight, s);
   m.listWithSubtitleRowHeight = sp(b.listWithSubtitleRowHeight, s);

src/components/themes/BaseTheme.h

@@ -110,7 +110,7 @@ struct ThemeMetrics {
 // Expected sizeof(ThemeMetrics), in bytes. scaleThemeMetrics() static_asserts
 // against this so a new/removed metric field can't slip through unclassified;
 // update it after adding a field (and decide there whether the field scales).
-inline constexpr unsigned THEME_METRICS_SIZEOF = 216;
+inline constexpr unsigned THEME_METRICS_SIZEOF = 224;
 
 enum UIIcon { None = 0, Folder, Text, Image, Book, File, Settings, Transfer, Library, Wifi, Hotspot, Bookmark, Firmware };