Update GUI styling and font configuration

- Fix bt_app.h syntax error (remove stray "1")
- Improve menu item alignment and styling
- Enable additional LVGL fonts (Montserrat 8, Unscii 16)
- Clean up volume page layout, remove instruction labels
- Update default font to Montserrat 8

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

sdkconfig

@@ -2246,13 +2246,13 @@ CONFIG_LV_ATTRIBUTE_MEM_ALIGN_SIZE=1
 #
 # Enable built-in fonts
 #
-# CONFIG_LV_FONT_MONTSERRAT_8 is not set
+CONFIG_LV_FONT_MONTSERRAT_8=y
 # CONFIG_LV_FONT_MONTSERRAT_10 is not set
-# CONFIG_LV_FONT_MONTSERRAT_12 is not set
+CONFIG_LV_FONT_MONTSERRAT_12=y
 CONFIG_LV_FONT_MONTSERRAT_14=y
 # CONFIG_LV_FONT_MONTSERRAT_16 is not set
 # CONFIG_LV_FONT_MONTSERRAT_18 is not set
-CONFIG_LV_FONT_MONTSERRAT_20=y
+# CONFIG_LV_FONT_MONTSERRAT_20 is not set
 # CONFIG_LV_FONT_MONTSERRAT_22 is not set
 # CONFIG_LV_FONT_MONTSERRAT_24 is not set
 # CONFIG_LV_FONT_MONTSERRAT_26 is not set
@@ -2272,10 +2272,10 @@ CONFIG_LV_FONT_MONTSERRAT_20=y
 # CONFIG_LV_FONT_SIMSUN_14_CJK is not set
 # CONFIG_LV_FONT_SIMSUN_16_CJK is not set
 CONFIG_LV_FONT_UNSCII_8=y
-# CONFIG_LV_FONT_UNSCII_16 is not set
+CONFIG_LV_FONT_UNSCII_16=y
 # end of Enable built-in fonts
 
-# CONFIG_LV_FONT_DEFAULT_MONTSERRAT_8 is not set
+CONFIG_LV_FONT_DEFAULT_MONTSERRAT_8=y
 # CONFIG_LV_FONT_DEFAULT_MONTSERRAT_10 is not set
 # CONFIG_LV_FONT_DEFAULT_MONTSERRAT_12 is not set
 # CONFIG_LV_FONT_DEFAULT_MONTSERRAT_14 is not set
@@ -2300,7 +2300,7 @@ CONFIG_LV_FONT_UNSCII_8=y
 # CONFIG_LV_FONT_DEFAULT_DEJAVU_16_PERSIAN_HEBREW is not set
 # CONFIG_LV_FONT_DEFAULT_SIMSUN_14_CJK is not set
 # CONFIG_LV_FONT_DEFAULT_SIMSUN_16_CJK is not set
-CONFIG_LV_FONT_DEFAULT_UNSCII_8=y
+# CONFIG_LV_FONT_DEFAULT_UNSCII_8 is not set
 # CONFIG_LV_FONT_DEFAULT_UNSCII_16 is not set
 # CONFIG_LV_FONT_FMT_TXT_LARGE is not set
 # CONFIG_LV_USE_FONT_COMPRESSED is not set