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>

main/bt_app.h

@@ -81,7 +81,7 @@ typedef struct {
 
 typedef struct {
     bt_device_info_t devices[MAX_BT_DEVICES];
-    int count;1 
+    int count;
     bool discovery_active;
 } bt_device_list_t;