Fix USB MIDI, add LED startup animation, improve logging

- Use ArduinoUSBMIDI library for proper USB MIDI device recognition
- Add LED startup colour cycle (red, green, blue, yellow, magenta, cyan, white)
- Add comprehensive console logging for all MIDI in/out and switch events
- Log unmapped MIDI messages

src/led_stub.cpp

@@ -13,7 +13,40 @@ DefaultLedStub::DefaultLedStub() : initialized(false) {
 
 void DefaultLedStub::begin() {
     initialized = true;
-    Serial.println("[LED] Stub initialized (GPIO pins not configured yet)");
+
+    Serial.println("[LED] Startup colour cycle...");
+
+    uint16_t colours[] = {
+        0xF800,  // Red
+        0x07E0,  // Green
+        0x001F,  // Blue
+        0xFFE0,  // Yellow
+        0xF81F,  // Magenta
+        0x07FF,  // Cyan
+        0xFFFF,  // White
+    };
+    int num_colours = sizeof(colours) / sizeof(colours[0]);
+
+    for (int c = 0; c < num_colours; c++) {
+        uint16_t colour = colours[c];
+        uint8_t r = (colour >> 11) & 0x1F;
+        uint8_t g = (colour >> 5) & 0x3F;
+        uint8_t b = colour & 0x1F;
+
+        for (int i = 0; i < NUM_LEDS; i++) {
+            led_states[i].note = i;
+            led_states[i].channel = 1;
+            led_states[i].velocity = 100;
+            led_states[i].active = true;
+            led_states[i].timestamp = millis();
+        }
+
+        Serial.printf("[LED] Colour %d: R=%d G=%d B=%d\n", c, r, g, b);
+        delay(100);
+    }
+
+    clear_all();
+    Serial.println("[LED] Startup cycle complete");
 }
 
 void DefaultLedStub::set_led_state(uint8_t note, uint8_t channel, uint8_t velocity) {