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/app_task.cpp

@@ -4,7 +4,6 @@
 AppTask::AppTask(LedStub* led, SwitchStub* sw, UsbMidiTransport* midi)
     : led_driver(led), switch_driver(sw), midi_transport(midi) {
     
-    // Default pad mapping
     for (uint8_t i = 0; i < NUM_PADS; i++) {
         pad_mapping[i].physical_switch = i;
         pad_mapping[i].midi_channel = 1;
@@ -15,23 +14,25 @@ AppTask::AppTask(LedStub* led, SwitchStub* sw, UsbMidiTransport* midi)
 }
 
 void AppTask::begin() {
-    Serial.println("[APP] Controller task started");
+    Serial.println("[APP] Registering MIDI callbacks...");
     
-    // Register MIDI callback
     midi_transport->on_midi_receive([this](const MidiEvent& event) {
         process_midi_event(event);
     });
+    
+    Serial.println("[APP] Controller ready");
 }
 
 void AppTask::update() {
-    // Poll switches
     for (uint8_t i = 0; i < NUM_PADS; i++) {
         bool is_pressed = switch_driver->is_pressed(i);
         
         if (is_pressed && !last_switch_state[i]) {
+            Serial.printf("[APP] Switch %d pressed\n", i);
             process_switch_event(i, true);
             last_switch_state[i] = true;
         } else if (!is_pressed && last_switch_state[i]) {
+            Serial.printf("[APP] Switch %d released\n", i);
             process_switch_event(i, false);
             last_switch_state[i] = false;
         }
@@ -44,7 +45,6 @@ void AppTask::process_midi_event(const MidiEvent& event) {
     uint8_t midi_note = event.data1;
     uint8_t midi_velocity = event.data2;
     
-    // Find matching LED index from pad mapping
     for (uint8_t i = 0; i < NUM_PADS; i++) {
         if (pad_mapping[i].midi_channel == midi_channel && 
             pad_mapping[i].midi_note == midi_note) {
@@ -62,11 +62,13 @@ void AppTask::process_midi_event(const MidiEvent& event) {
         
         Serial.printf("[APP] MIDI -> LED: Ch%d Note%d Vel%d -> LED%d\n",
                       midi_channel, midi_note, midi_velocity, led_index);
+    } else {
+        Serial.printf("[APP] MIDI Ch%d Note%d Vel%d - no LED mapping\n",
+                      midi_channel, midi_note, midi_velocity);
     }
 }
 
 void AppTask::process_switch_event(uint8_t switch_id, bool pressed) {
-    // Find mapping for this switch
     for (uint8_t i = 0; i < NUM_PADS; i++) {
         if (pad_mapping[i].physical_switch == switch_id) {
             uint8_t channel = pad_mapping[i].midi_channel;