fix(lockscreen): correct main.cpp injection anchor and early-return guard

plugins/lockscreen/LockscreenSettingsPage.h

@@ -0,0 +1,11 @@
+#pragma once
+
+#include <GfxRenderer.h>
+#include "LockscreenPlugin.h"
+
+class LockscreenSettingsActivity {
+public:
+    static void render(GfxRenderer& renderer, LockscreenMode currentMode);
+    static LockscreenMode handleNext(LockscreenMode currentMode);
+    static LockscreenMode handlePrev(LockscreenMode currentMode);
+};