fix: Add destruction callback to EmulatedController for safe pointer management

Add SetDestructionCallback() method to allow observers to safely null
out pointers when the controller is destroyed. This prevents use-after-free
issues in UI components.

Also includes cleanup and const correctness improvements in
configure_input_player_widget.

Signed-off-by: Zephyron <zephyron@citron-emu.org>

src/hid_core/frontend/emulated_controller.cpp

@@ -24,7 +24,15 @@ constexpr Common::UUID VIRTUAL_UUID =
 
 EmulatedController::EmulatedController(NpadIdType npad_id_type_) : npad_id_type(npad_id_type_) {}
 
-EmulatedController::~EmulatedController() = default;
+EmulatedController::~EmulatedController() {
+    if (destruction_callback) {
+        destruction_callback();
+    }
+}
+
+void EmulatedController::SetDestructionCallback(std::function<void()> callback) {
+    destruction_callback = std::move(callback);
+}
 
 NpadStyleIndex EmulatedController::MapSettingsTypeToNPad(Settings::ControllerType type) {
     switch (type) {

src/hid_core/frontend/emulated_controller.h

@@ -473,6 +473,12 @@ public:
     /// Changes sensitivity of the motion sensor
     void SetGyroscopeZeroDriftMode(GyroscopeZeroDriftMode mode);
 
+    /**
+     * Sets a callback to be invoked when this object is about to be destructed.
+     * This is used for observers to safely null out their pointers.
+     */
+    void SetDestructionCallback(std::function<void()> callback);
+
     /**
      * Adds a callback to the list of events
      * @param update_callback A ConsoleUpdateCallback that will be triggered
@@ -654,6 +660,8 @@ private:
     std::unordered_map<int, ControllerUpdateCallback> callback_list;
     int last_callback_key = 0;
 
+    std::function<void()> destruction_callback;
+
     // Stores the current status of all controller input
     ControllerStatus controller;
 };