Refactor RootLayout and UIHandler for improved structure and functionality

- Updated RootLayout to manage layout initialization and deinitialization more effectively.
- Removed unnecessary dependencies and streamlined event handling for keyboard events.
- Enhanced UIHandler to utilize shared pointers for app descriptors, improving memory management.
- Added methods for showing and hiding navigation elements in RootLayout.
- Introduced textarea widget with instant response by disabling animations.
- Improved error handling and logging throughout the UI components.

main/ui/apps/app.h

@@ -0,0 +1,87 @@
+#pragma once
+
+#include "lvgl.h"
+#include "esp_err.h"
+#include <string>
+#include <memory>
+
+/**
+ * @brief Base class for all UI applications
+ *
+ * All UI applications (apps) must inherit from this class.
+ * Each app is responsible for managing its own widgets within
+ * the provided LVGL container. The UIHandler will manage the
+ * lifecycle of apps and event routing.
+ */
+class UIApp {
+public:
+  virtual ~UIApp() = default;
+
+  /**
+   * @brief Initialize the app with the given container
+   *
+   * The app should create all its widgets as children of the
+   * provided container. The container is already positioned
+   * between the header and navigation bar.
+   *
+   * @param container LVGL container object for this app
+   * @return ESP_OK on success, error code otherwise
+   */
+  virtual esp_err_t init(lv_obj_t* container) = 0;
+
+  /**
+   * @brief Deinitialize and clean up app resources
+   *
+   * The app should delete all widgets and release any resources.
+   * The container itself will be handled by UIHandler.
+   *
+   * @return ESP_OK on success, error code otherwise
+   */
+  virtual esp_err_t deinit(void) = 0;
+
+  /**
+   * @brief Get the display name of this app
+   *
+   * Used for logging and potentially showing in navigation.
+   *
+   * @return std::string app name
+   */
+  virtual std::string get_name(void) const = 0;
+
+  /**
+   * @brief Handle back button press
+   *
+   * Called when the back button is pressed.
+   * The app can choose to handle it (e.g., close a dialog)
+   * or return false to let UIHandler handle it (e.g., return to main screen).
+   *
+   * @return true if the event was handled, false otherwise
+   */
+  virtual bool on_back_button_pressed(void) {
+    return false; // default: not handled
+  }
+
+protected:
+  lv_obj_t* container_ = nullptr;  ///< LVGL container provided by UIHandler
+};
+
+class AppDescriptor {
+public:
+  virtual ~AppDescriptor() = default;
+  virtual void draw_icon(lv_obj_t* parent) = 0;
+
+  std::string get_name() const {
+    return name_;
+  }
+
+  UIApp* get_app_instance() const {
+    return app_instance_.get();
+  }
+
+protected:
+  AppDescriptor(std::string name, std::unique_ptr<UIApp> app_instance)
+    : name_(name), app_instance_(std::move(app_instance)) { }
+
+  std::string name_;
+  std::unique_ptr<UIApp> app_instance_;
+};