add HalPowerManager

lib/hal/HalPowerManager.h

@@ -0,0 +1,26 @@
+#pragma once
+
+#include <Arduino.h>
+#include <BatteryMonitor.h>
+#include <InputManager.h>
+
+#include "HalGPIO.h"
+
+class HalPowerManager {
+  static constexpr int LOW_POWER_FREQ = 10; // MHz
+
+  int normalFreq = 0; // MHz
+  bool isLowPower = false;
+
+ public:
+  void begin();
+
+  // Control CPU frequency for power saving
+  void setPowerSaving(bool enabled);
+
+  // Setup wake up GPIO and enter deep sleep
+  void startDeepSleep(HalGPIO &gpio) const;
+
+  // Get battery percentage (range 0-100)
+  int getBatteryPercentage() const;
+};