Add VID/PID to build flags for ESP32 core + stronger visual indicators

- Set USB VID/PID via ESP32 core build flags (may work better than TinyUSB API)
- Heartbeat on LED 9 (amber pulse every 2s) confirms device is alive
- SysEx flashes ALL LEDs white for 200ms
- Regular MIDI flashes LED 0 white for 50ms

platformio.ini

@@ -16,6 +16,10 @@ build_flags =
     -DARDUINO_USB_MODE=0
     -DARDUINO_USB_CDC_ON_BOOT=1
     -DUSE_TINYUSB=1
+    -DUSB_VID=0x1235
+    -DUSB_PID=0x0103
+    -DUSB_MANUFACTURER="Novation"
+    -DUSB_PRODUCT="Launchpad X"
 
 monitor_speed = 115200