fix: Use HalPowerManager for battery percentage (#1005)

## Summary

The introduction of `HalGPIO` moved the `BatteryMonitor battery` object
into the member function `HalGPIO::getBatteryPercentage()`.

Then, with the introduction of `HalPowerManager`, this function was
moved to `HalPowerManager::getBatteryPercentage()`.

However, the original `BatteryMonitor battery` object is still utilized
by themes for displaying the battery percentage.

This PR replaces these deprecated uses of `BatteryMonitor battery` with
the new `HalPowerManager::getBatteryPercentage()` function.

---

### AI Usage

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please be transparent about their usage as it
helps set the right context for reviewers.

Did you use AI tools to help write this code? _**NO **_

src/Battery.h

@@ -1,6 +0,0 @@
-#pragma once
-#include <BatteryMonitor.h>
-
-#define BAT_GPIO0 0  // Battery voltage
-
-static BatteryMonitor battery(BAT_GPIO0);

src/activities/home/HomeActivity.cpp

@@ -11,7 +11,6 @@
 #include <cstring>
 #include <vector>
 
-#include "Battery.h"
 #include "CrossPointSettings.h"
 #include "CrossPointState.h"
 #include "MappedInputManager.h"

src/components/themes/BaseTheme.cpp

@@ -1,6 +1,7 @@
 #include "BaseTheme.h"
 
 #include <GfxRenderer.h>
+#include <HalPowerManager.h>
 #include <HalStorage.h>
 #include <Logging.h>
 #include <Utf8.h>
@@ -8,7 +9,6 @@
 #include <cstdint>
 #include <string>
 
-#include "Battery.h"
 #include "I18n.h"
 #include "RecentBooksStore.h"
 #include "components/UITheme.h"
@@ -47,7 +47,7 @@ void drawBatteryIcon(const GfxRenderer& renderer, int x, int y, int battWidth, i
 
 void BaseTheme::drawBatteryLeft(const GfxRenderer& renderer, Rect rect, const bool showPercentage) const {
   // Left aligned: icon on left, percentage on right (reader mode)
-  const uint16_t percentage = battery.readPercentage();
+  const uint16_t percentage = powerManager.getBatteryPercentage();
   const int y = rect.y + 6;
 
   if (showPercentage) {
@@ -62,7 +62,7 @@ void BaseTheme::drawBatteryLeft(const GfxRenderer& renderer, Rect rect, const bo
 void BaseTheme::drawBatteryRight(const GfxRenderer& renderer, Rect rect, const bool showPercentage) const {
   // Right aligned: percentage on left, icon on right (UI headers)
   // rect.x is already positioned for the icon (drawHeader calculated it)
-  const uint16_t percentage = battery.readPercentage();
+  const uint16_t percentage = powerManager.getBatteryPercentage();
   const int y = rect.y + 6;
 
   if (showPercentage) {

src/components/themes/lyra/LyraTheme.cpp

@@ -1,13 +1,13 @@
 #include "LyraTheme.h"
 
 #include <GfxRenderer.h>
+#include <HalPowerManager.h>
 #include <HalStorage.h>
 #include <I18n.h>
 
 #include <cstdint>
 #include <string>
 
-#include "Battery.h"
 #include "RecentBooksStore.h"
 #include "components/UITheme.h"
 #include "components/icons/book.h"
@@ -85,7 +85,7 @@ const uint8_t* iconForName(UIIcon icon, int size) {
 
 void LyraTheme::drawBatteryLeft(const GfxRenderer& renderer, Rect rect, const bool showPercentage) const {
   // Left aligned: icon on left, percentage on right (reader mode)
-  const uint16_t percentage = battery.readPercentage();
+  const uint16_t percentage = powerManager.getBatteryPercentage();
   const int y = rect.y + 6;
   const int battWidth = LyraMetrics::values.batteryWidth;
 
@@ -122,7 +122,7 @@ void LyraTheme::drawBatteryLeft(const GfxRenderer& renderer, Rect rect, const bo
 
 void LyraTheme::drawBatteryRight(const GfxRenderer& renderer, Rect rect, const bool showPercentage) const {
   // Right aligned: percentage on left, icon on right (UI headers)
-  const uint16_t percentage = battery.readPercentage();
+  const uint16_t percentage = powerManager.getBatteryPercentage();
   const int y = rect.y + 6;
   const int battWidth = LyraMetrics::values.batteryWidth;
 

src/main.cpp

@@ -13,7 +13,6 @@
 
 #include <cstring>
 
-#include "Battery.h"
 #include "CrossPointSettings.h"
 #include "CrossPointState.h"
 #include "KOReaderCredentialStore.h"