Fix Phase 1 skeleton: add build system, fix compilation errors

- Add CMakeLists.txt for project and all components
- Add idf_component.yml with TinyUSB dependency
- Create switch_stub.cpp implementation
- Fix app_task.h to match .cpp implementation (2-param signature)
- Fix led_stub.h/cpp class naming (DefaultLedStub)
- Fix midi_transport.cpp TinyUSB API usage (tud_midi_*)
- Move main.cpp to main/ directory
- Add sdkconfig.defaults for ESP32-S3

sdkconfig.defaults

@@ -0,0 +1,16 @@
+# ESP32-S3 Configuration
+CONFIG_IDF_TARGET="esp32s3"
+
+# USB Configuration
+CONFIG_TINYUSB_DESC_MANUFACTURER_STRING="Ashley Strahle"
+CONFIG_TINYUSB_DESC_PRODUCT_STRING="Loopy Foot Controller"
+CONFIG_TINYUSB_DESC_CDC_STRING="Loopy Foot Controller"
+CONFIG_TINYUSB_MIDI_ENABLED=y
+CONFIG_TINYUSB_MIDI_RX_BUFSIZE=64
+CONFIG_TINYUSB_MIDI_TX_BUFSIZE=64
+
+# FreeRTOS
+CONFIG_FREERTOS_HZ=1000
+
+# Log level
+CONFIG_LOG_DEFAULT_LEVEL_INFO=y