feat: Implement Discord app UI and settings management

- Added MainUI class for displaying voice state, status icon, and buttons.
- Introduced MainUIHandler to manage UI interactions and bridge communication.
- Created SettingsUI for displaying QR code and configuration instructions.
- Implemented SettingsUIHandler to manage settings and web server interactions.
- Developed WebHandler for handling HTTP requests for settings configuration.
- Updated AppRegistry to initialize with the new Discord app descriptor.
- Enhanced InteractionHandler to support keyboard interactions across app switches.
- Updated UIHandler to manage app switching and rendering of app icons.
- Enabled QR code support in LVGL configuration.

main/ui/apps/registry.cpp

@@ -0,0 +1,9 @@
+#include "ui/apps/registry.h"
+
+#include "ui/apps/iotdis/descriptor.h"
+
+esp_err_t AppRegistry::init(void) {
+  register_app(std::make_unique<IotDisDescriptor>());
+
+  return ESP_OK;
+}