Add Application-level NetworkMonitor with extensive logging

- Create SimpleNotesApplication class for app-level lifecycle
- Move NetworkMonitor from Activity to Application context
- Add comprehensive logging to NetworkMonitor (all callbacks)
- Add logging to SyncWorker for debugging
- Remove NetworkMonitor from MainActivity (now in Application)
- Add Battery Optimization dialog in SettingsActivity
- Improve Notifications (showSyncInProgress, showSyncSuccess, showSyncError)

This should fix background sync issues - NetworkMonitor now runs
with Application context instead of Activity context, which should
survive when app is in background.

Debug with: adb logcat | grep -E 'NetworkMonitor|SyncWorker|SimpleNotesApp'

android/app/src/main/AndroidManifest.xml

@@ -7,8 +7,10 @@
     <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
     <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
     <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
+    <uses-permission android:name="android.permission.REQUEST_IGNORE_BATTERY_OPTIMIZATIONS" />
 
     <application
+        android:name=".SimpleNotesApplication"
         android:allowBackup="true"
         android:dataExtractionRules="@xml/data_extraction_rules"
         android:fullBackupContent="@xml/backup_rules"
@@ -39,16 +41,6 @@
             android:name=".SettingsActivity"
             android:parentActivityName=".MainActivity" />
 
-        <!-- WiFi Sync Receiver -->
-        <receiver
-            android:name=".sync.WifiSyncReceiver"
-            android:exported="false">
-            <intent-filter>
-                <action android:name="android.net.wifi.STATE_CHANGE" />
-                <action android:name="android.net.conn.CONNECTIVITY_CHANGE" />
-            </intent-filter>
-        </receiver>
-
     </application>
 
 </manifest>