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

plugins/lockscreen/LockscreenPlugin.h

@@ -0,0 +1,19 @@
+#pragma once
+
+#include <Arduino.h>
+
+enum class LockscreenMode : uint8_t {
+    MODE_OFF = 0,
+    ENABLED  = 1,
+};
+
+namespace LockscreenPlugin {
+
+const char* modeName(LockscreenMode mode);
+bool shouldLock(LockscreenMode mode);
+bool shouldLockOnWake(LockscreenMode mode);
+bool shouldLockOnPower(LockscreenMode mode);
+void hashPin(const char* pin, char outHash[9]);
+bool checkPin(const char* pin, const char* storedHash);
+
+}