feat(rlcd): runtime font size selector in Settings->Display

- device.properties bump default to 20
- lvgl_fonts add runtime override API (g_runtime_font_size + externs for all Montserrat sizes)
- DisplaySettings add fontSize field persisted in properties
- Display app adds Font size dropdown 14-28 applying immediately
- Lvgl.cpp applies saved runtime font on boot
- device.py new bucket <=20 includes all fonts for runtime switching (~150KB)

Co-authored-by: internal-model

Tactility/Source/lvgl/Lvgl.cpp

@@ -11,6 +11,7 @@
 #include <Tactility/settings/DisplaySettings.h>
 
 #include <tactility/lvgl_module.h>
+#include <tactility/lvgl_fonts.h>
 #include <tactility/module.h>
 
 #include <lvgl.h>
@@ -44,6 +45,11 @@ void attachDevices() {
                 if (rotation != lv_display_get_rotation(lvgl_display)) {
                     lv_display_set_rotation(lvgl_display, rotation);
                 }
+                // Apply runtime font size (0 = compile-time default)
+                if (settings.fontSize != 0) {
+                    lvgl_set_runtime_font_size(settings.fontSize);
+                    LOGGER.info("Runtime font size set to {}", settings.fontSize);
+                }
                 // Apply invert setting if display supports it
                 if (display->supportsInvertColor()) {
                     display->setInvertColor(settings.invertColor);