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/iotdis/app.h

@@ -0,0 +1,61 @@
+#pragma once
+
+#include "ui/apps/app.h"
+#include "ui/apps/iotdis/settings/settings_handler.h"
+#include "ui/apps/iotdis/ui/main_handler.h"
+#include "ui/apps/iotdis/ui/settings_handler.h"
+#include "io/nvs_handler.h"
+#include <string>
+#include <memory>
+
+// Forward declarations
+class MainUIHandler;
+class SettingsUIHandler;
+
+/**
+ * @brief IotDis (Discord Integration) App
+ *
+ * Manages Discord voice state monitoring and control via UDP bridge.
+ * Features:
+ * - Real-time voice state monitoring (muted/unmuted)
+ * - Manual mute/unmute control
+ * - Settings for bridge IP/port configuration
+ * - Connection error detection and notification
+ * - NVS storage for persistent settings
+ */
+class IotDisApp : public UIApp {
+public:
+  IotDisApp();
+  ~IotDisApp() override;
+
+  esp_err_t init(lv_obj_t* container, InteractionHandler* interaction_handler) override;
+  esp_err_t deinit(void) override;
+  std::string get_name(void) const override;
+  bool on_back_button_pressed(void) override;
+
+private:
+  // UI handlers
+  std::unique_ptr<MainUIHandler> main_ui_handler_;
+  std::unique_ptr<SettingsUIHandler> settings_ui_handler_;
+
+  // Current page tracking
+  enum class Page {
+    MAIN,
+    SETTINGS
+  };
+  Page current_page_;
+
+  // Settings handler (shared across handlers)
+  std::unique_ptr<SettingHandler> setting_handler_;
+
+  // Interaction handler (not owned)
+  InteractionHandler* interaction_handler_;
+
+  static constexpr const char* NVS_NAMESPACE = "discord_app";
+
+  // Private methods
+  void show_settings_page();
+
+  // UI callback forwarders
+  static void on_settings_button_clicked_static(lv_event_t* e);
+};