Prioritize private payload for battery info in single headset devices

This commit modifies `SingleApplePods`, `AirPodsMaxUsbc`, and `AirPodsMax` to prioritize battery information from the decrypted private payload when available.

Specifically:
- `SingleApplePods.batteryHeadsetPercent`: Now checks `payload.private?.asBatteryState(1)?.level` first. If the private payload is not available or doesn't contain battery information at position 1, it falls back to the existing logic using `pubPodsBattery`.
- `AirPodsMaxUsbc.isHeadsetBeingCharged` and `AirPodsMax.isHeadsetBeingCharged`: Now check `payload.private?.asBatteryState(1)?.isCharging` first. If the private payload is not available or doesn't contain charging status at position 1, they fall back to the existing logic using `pubFlags.isBitSet(0)`.

This change allows for more accurate battery level and charging status reporting when the private payload can be decrypted.

app-common/src/main/java/eu/darken/capod/pods/core/apple/SingleApplePods.kt

@@ -10,13 +10,18 @@ import eu.darken.capod.pods.core.SinglePodDevice
 interface SingleApplePods : ApplePods, SinglePodDevice, HasAppleColor {
 
     override val batteryHeadsetPercent: Float?
-        get() = when (val value = pubPodsBattery.lowerNibble.toInt()) {
-            15 -> null
-            else -> if (value > 10) {
-                log { "Headset above 100% battery: $value" }
-                1.0f
-            } else {
-                (value / 10f)
+        get() {
+            payload.private?.asBatteryState(1)?.let {
+                return it.level
+            }
+            return when (val value = pubPodsBattery.lowerNibble.toInt()) {
+                15 -> null
+                else -> if (value > 10) {
+                    log { "Headset above 100% battery: $value" }
+                    1.0f
+                } else {
+                    (value / 10f)
+                }
             }
         }
 }

app-common/src/main/java/eu/darken/capod/pods/core/apple/airpods/AirPodsMax.kt

@@ -35,7 +35,12 @@ data class AirPodsMax(
         get() = rssiAverage ?: super<SingleApplePods>.rssi
 
     override val isHeadsetBeingCharged: Boolean
-        get() = pubFlags.isBitSet(0)
+        get() {
+            payload.private?.asBatteryState(1)?.let {
+                return it.isCharging
+            }
+            return pubFlags.isBitSet(0)
+        }
 
     override val isBeingWorn: Boolean
         get() = pubStatus.isBitSet(5)

app-common/src/main/java/eu/darken/capod/pods/core/apple/airpods/AirPodsMaxUsbc.kt

@@ -35,7 +35,12 @@ data class AirPodsMaxUsbc(
         get() = rssiAverage ?: super<SingleApplePods>.rssi
 
     override val isHeadsetBeingCharged: Boolean
-        get() = pubFlags.isBitSet(0)
+        get() {
+            payload.private?.asBatteryState(1)?.let {
+                return it.isCharging
+            }
+            return pubFlags.isBitSet(0)
+        }
 
     override val isBeingWorn: Boolean
         get() = pubStatus.isBitSet(5)