Refactor LVGL code into kernel module (#472)

* **New Features**
  * Added a standalone LVGL module and enabled LVGL support in the simulator for richer local UI testing.

* **Refactor**
  * HAL and LVGL split into distinct modules; startup and device attach/detach flows reorganized for clearer lifecycle management.
  * Public APIs tightened with clearer nullability/documentation.

* **Bug Fixes**
  * More consistent LVGL start/stop and device attach/detach behavior for improved stability.

Drivers/ButtonControl/Source/ButtonControl.h

@@ -37,7 +37,7 @@ private:
         bool triggerLongPress = false;
     };
 
-    lv_indev_t* _Nullable deviceHandle = nullptr;
+    lv_indev_t* deviceHandle = nullptr;
     std::shared_ptr<tt::Thread> driverThread;
     bool interruptDriverThread = false;
     tt::Mutex mutex;
@@ -67,7 +67,8 @@ public:
     bool startLvgl(lv_display_t* display) override;
     bool stopLvgl() override;
 
-    lv_indev_t* _Nullable getLvglIndev() override { return deviceHandle; }
+    /** Could return nullptr if not started */
+    lv_indev_t* getLvglIndev() override { return deviceHandle; }
 
     static std::shared_ptr<ButtonControl> createOneButtonControl(tt::hal::gpio::Pin pin) {
         return std::make_shared<ButtonControl>(std::vector {

Drivers/CST816S/Source/Cst816Touch.h

@@ -49,7 +49,7 @@ private:
     std::unique_ptr<Configuration> configuration;
     esp_lcd_panel_io_handle_t ioHandle = nullptr;
     esp_lcd_touch_handle_t touchHandle = nullptr;
-    lv_indev_t* _Nullable deviceHandle = nullptr;
+    lv_indev_t* deviceHandle = nullptr;
 
     void cleanup();
 

Drivers/EspLcdCompat/Source/EspLcdDisplay.h

@@ -10,10 +10,10 @@
 /** @deprecated use EspLcdDisplayV2 */
 class EspLcdDisplay : public tt::hal::display::DisplayDevice {
 
-    esp_lcd_panel_io_handle_t _Nullable ioHandle = nullptr;
-    esp_lcd_panel_handle_t _Nullable panelHandle = nullptr;
-    lv_display_t* _Nullable lvglDisplay = nullptr;
-    std::shared_ptr<tt::hal::display::DisplayDriver> _Nullable displayDriver;
+    esp_lcd_panel_io_handle_t ioHandle = nullptr;
+    esp_lcd_panel_handle_t panelHandle = nullptr;
+    lv_display_t* lvglDisplay = nullptr;
+    std::shared_ptr<tt::hal::display::DisplayDriver> displayDriver;
     std::shared_ptr<tt::Lock> lock;
     lcd_rgb_element_order_t rgbElementOrder;
 
@@ -52,7 +52,7 @@ public:
 
     bool stopLvgl() final;
 
-    lv_display_t* _Nullable getLvglDisplay() const final { return lvglDisplay; }
+    lv_display_t* getLvglDisplay() const final { return lvglDisplay; }
 
     // endregion
 
@@ -61,7 +61,7 @@ public:
     bool supportsDisplayDriver() const override { return true; }
 
     /** @return a NativeDisplay instance if this device supports it */
-    std::shared_ptr<tt::hal::display::DisplayDriver> _Nullable getDisplayDriver() final;
+    std::shared_ptr<tt::hal::display::DisplayDriver> getDisplayDriver() final;
 
     // endregion
 };

Drivers/EspLcdCompat/Source/EspLcdTouch.h

@@ -11,7 +11,7 @@ class EspLcdTouch : public tt::hal::touch::TouchDevice {
     esp_lcd_touch_config_t config;
     esp_lcd_panel_io_handle_t _Nullable ioHandle = nullptr;
     esp_lcd_touch_handle_t _Nullable touchHandle = nullptr;
-    lv_indev_t* _Nullable lvglDevice = nullptr;
+    lv_indev_t* lvglDevice = nullptr;
     std::shared_ptr<tt::hal::touch::TouchDriver> touchDriver;
 
 protected:
@@ -36,7 +36,7 @@ public:
 
     bool stopLvgl() final;
 
-    lv_indev_t* _Nullable getLvglIndev() final { return lvglDevice; }
+    lv_indev_t* getLvglIndev() final { return lvglDevice; }
 
     bool supportsTouchDriver() override { return true; }
 

Drivers/FT6x36/Source/Ft6x36Touch.h

@@ -34,7 +34,7 @@ public:
 private:
 
     std::unique_ptr<Configuration> configuration;
-    lv_indev_t* _Nullable deviceHandle = nullptr;
+    lv_indev_t* deviceHandle = nullptr;
     FT6X36 driver = FT6X36(configuration->port, configuration->pinInterrupt);
     std::shared_ptr<tt::Thread> driverThread;
     bool interruptDriverThread = false;
@@ -65,7 +65,7 @@ public:
     bool startLvgl(lv_display_t* display) override;
     bool stopLvgl() override;
 
-    lv_indev_t* _Nullable getLvglIndev() override { return deviceHandle; }
+    lv_indev_t* getLvglIndev() override { return deviceHandle; }
 
     class Ft6TouchDriver : public tt::hal::touch::TouchDriver {
     public:

Drivers/ILI934x/Source/Ili934xDisplay.h

@@ -25,7 +25,7 @@ public:
         bool swapBytes;
         uint32_t bufferSize; // Pixel count, not byte count. Set to 0 for default (1/10th of display size)
         std::shared_ptr<tt::hal::touch::TouchDevice> touch;
-        std::function<void(uint8_t)> _Nullable backlightDutyFunction;
+        std::function<void(uint8_t)> backlightDutyFunction; // Nullable
         gpio_num_t resetPin;
         lcd_rgb_element_order_t rgbElementOrder;
     };