feat(ios): implement getBatteryStatus method

Implemented battery status method matching Android functionality:

getBatteryStatus():
- Gets battery level (0-100%) using UIDevice
- Detects charging state (charging or full)
- Maps battery state to power state code (0=unknown, 1=unplugged, 2=charging, 3=full)
- Returns isOptimizationExempt (always false on iOS - no battery optimization)
- Enables battery monitoring automatically

iOS Adaptations:
- Uses UIDevice.current for battery information
- Battery optimization not applicable on iOS (Background App Refresh is system setting)
- Returns -1 for battery level if unknown

Progress: 16/52 methods implemented (31% complete)

ios/Plugin/DailyNotificationPlugin.swift

@@ -11,6 +11,7 @@ import Capacitor
 import UserNotifications
 import BackgroundTasks
 import CoreData
+import UIKit
 
 /**
  * iOS implementation of Daily Notification Plugin
@@ -608,6 +609,64 @@ public class DailyNotificationPlugin: CAPPlugin {
         requestNotificationPermissions(call)
     }
     
+    /**
+     * Get battery status
+     * 
+     * Returns battery information including:
+     * - level: Battery level (0-100)
+     * - isCharging: Whether device is charging
+     * - powerState: Power state code
+     * - isOptimizationExempt: Whether app is exempt from battery optimization (iOS: always false)
+     * 
+     * Equivalent to Android's getBatteryStatus method.
+     */
+    @objc func getBatteryStatus(_ call: CAPPluginCall) {
+        print("DNP-PLUGIN: Getting battery status")
+        
+        // Enable battery monitoring if not already enabled
+        UIDevice.current.isBatteryMonitoringEnabled = true
+        
+        // Get battery level (0.0 to 1.0, -1.0 if unknown)
+        let batteryLevel = UIDevice.current.batteryLevel
+        let batteryLevelPercent = batteryLevel >= 0 ? Int(batteryLevel * 100) : -1
+        
+        // Get battery state
+        let batteryState = UIDevice.current.batteryState
+        let isCharging = batteryState == .charging || batteryState == .full
+        
+        // Map battery state to power state code
+        // 0 = unknown, 1 = unplugged, 2 = charging, 3 = full
+        let powerState: Int
+        switch batteryState {
+        case .unknown:
+            powerState = 0
+        case .unplugged:
+            powerState = 1
+        case .charging:
+            powerState = 2
+        case .full:
+            powerState = 3
+        @unknown default:
+            powerState = 0
+        }
+        
+        // iOS doesn't have battery optimization like Android
+        // Background App Refresh is the closest equivalent, but we can't check it directly
+        // Return false to indicate we're subject to system power management
+        let isOptimizationExempt = false
+        
+        let result: [String: Any] = [
+            "level": batteryLevelPercent,
+            "isCharging": isCharging,
+            "powerState": powerState,
+            "isOptimizationExempt": isOptimizationExempt
+        ]
+        
+        print("DNP-PLUGIN: Battery status: level=\(batteryLevelPercent)%, charging=\(isCharging), state=\(powerState)")
+        
+        call.resolve(result)
+    }
+    
     // MARK: - Private Implementation Methods
     
     private func setupBackgroundTasks() {