Fix USB MIDI, add GPIO for switches and LEDs

- Remove TinyUSBDevice.begin() conflict with Arduino core
- Switch stub now reads GPIO with debounce (pins 1-10)
- LED stub now drives GPIO pins (pins 11-20) with startup animation
- All pins printed to console on init

src/led_stub.cpp

@@ -1,6 +1,10 @@
 #include "led_stub.h"
 #include <Arduino.h>
 
+static const uint8_t LED_PINS[10] = {
+    11, 12, 13, 14, 15, 16, 17, 18, 19, 20
+};
+
 DefaultLedStub::DefaultLedStub() : initialized(false) {
     for (int i = 0; i < NUM_LEDS; i++) {
         led_states[i].active = false;
@@ -12,39 +16,25 @@ DefaultLedStub::DefaultLedStub() : initialized(false) {
 }
 
 void DefaultLedStub::begin() {
+    for (int i = 0; i < NUM_LEDS; i++) {
+        pinMode(LED_PINS[i], OUTPUT);
+        digitalWrite(LED_PINS[i], LOW);
+    }
     initialized = true;
 
     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);
+    for (int i = 0; i < NUM_LEDS; i++) {
+        digitalWrite(LED_PINS[i], HIGH);
+        Serial.printf("[LED] LED %d ON (GPIO %d)\n", i, LED_PINS[i]);
         delay(100);
     }
 
+    for (int i = 0; i < NUM_LEDS; i++) {
+        digitalWrite(LED_PINS[i], LOW);
+        delay(50);
+    }
+
     clear_all();
     Serial.println("[LED] Startup cycle complete");
 }
@@ -60,6 +50,8 @@ void DefaultLedStub::set_led_state(uint8_t note, uint8_t channel, uint8_t veloci
         led_states[led_index].velocity = velocity;
         led_states[led_index].active = (velocity > 0);
         led_states[led_index].timestamp = millis();
+
+        digitalWrite(LED_PINS[led_index], velocity > 0 ? HIGH : LOW);
         
         Serial.printf("[LED] Note %d -> LED %d Ch %d Vel %d (%s)\n",
                       note, led_index, channel, velocity,
@@ -73,6 +65,9 @@ void DefaultLedStub::clear_all() {
     for (int i = 0; i < NUM_LEDS; i++) {
         led_states[i].active = false;
         led_states[i].velocity = 0;
+        if (initialized) {
+            digitalWrite(LED_PINS[i], LOW);
+        }
     }
     Serial.println("[LED] All LEDs cleared");
 }