Fixed memory leak on API level 24.

*  When the application goes in the background from `ZimHostFragment`, `KiwixReaderFragment/ZimHostFragment` without starting the Service then the `ReadAloudService`, and `HotspotService` variables are not used and GC try to clear those objects but we are not clearing those objects, that's why memory leak is happening. So now we have free those objects if they are not in use.

core/src/main/java/org/kiwix/kiwixmobile/core/main/CoreReaderFragment.kt

@@ -333,6 +333,7 @@ abstract class CoreReaderFragment :
   private var readAloudService: ReadAloudService? = null
   private var navigationHistoryList: MutableList<NavigationHistoryListItem> = ArrayList()
   private var isReadSelection = false
+  private var isReadAloudServiceRunning = false
 
   private var storagePermissionForNotesLauncher: ActivityResultLauncher<String>? =
     registerForActivityResult(
@@ -1047,8 +1048,7 @@ abstract class CoreReaderFragment :
     } catch (ignore: IllegalArgumentException) {
       // to handle if service is already unbounded
     }
-    readAloudService?.registerCallBack(null)
+    unRegisterReadAloudService()
-    readAloudService = null
     storagePermissionForNotesLauncher?.unregister()
     storagePermissionForNotesLauncher = null
   }
@@ -2074,9 +2074,17 @@ abstract class CoreReaderFragment :
   private fun unbindService() {
     readAloudService?.let {
       requireActivity().unbindService(serviceConnection)
+      if (!isReadAloudServiceRunning) {
+        unRegisterReadAloudService()
+      }
     }
   }
 
+  private fun unRegisterReadAloudService() {
+    readAloudService?.registerCallBack(null)
+    readAloudService = null
+  }
+
   private fun createReadAloudIntent(action: String, isPauseTTS: Boolean): Intent =
     Intent(requireActivity(), ReadAloudService::class.java).apply {
       setAction(action)
@@ -2086,7 +2094,11 @@ abstract class CoreReaderFragment :
     }
 
   private fun setActionAndStartTTSService(action: String, isPauseTTS: Boolean = false) {
-    requireActivity().startService(createReadAloudIntent(action, isPauseTTS))
+    requireActivity().startService(
+      createReadAloudIntent(action, isPauseTTS)
+    ).also {
+      isReadAloudServiceRunning = action == ACTION_PAUSE_OR_RESUME_TTS
+    }
   }
 
   protected abstract fun restoreViewStateOnValidJSON(

core/src/main/java/org/kiwix/kiwixmobile/core/webserver/ZimHostFragment.kt

@@ -94,6 +94,7 @@ class ZimHostFragment : BaseFragment(), ZimHostCallbacks, ZimHostContract.View {
   private lateinit var serviceConnection: ServiceConnection
   private var dialog: Dialog? = null
   private var activityZimHostBinding: ActivityZimHostBinding? = null
+  private var isHotspotServiceRunning = false
   override val fragmentTitle: String? by lazy {
     getString(R.string.menu_wifi_hotspot)
   }
@@ -304,7 +305,11 @@ class ZimHostFragment : BaseFragment(), ZimHostCallbacks, ZimHostContract.View {
   }
 
   private fun stopServer() {
-    requireActivity().startService(createHotspotIntent(ACTION_STOP_SERVER))
+    requireActivity().startService(
+      createHotspotIntent(ACTION_STOP_SERVER)
+    ).also {
+      isHotspotServiceRunning = false
+    }
   }
 
   private fun select(bookOnDisk: BooksOnDiskListItem.BookOnDisk) {
@@ -341,6 +346,9 @@ class ZimHostFragment : BaseFragment(), ZimHostCallbacks, ZimHostContract.View {
   private fun unbindService() {
     hotspotService?.let {
       requireActivity().unbindService(serviceConnection)
+      if (!isHotspotServiceRunning) {
+        unRegisterHotspotService()
+      }
     }
   }
 
@@ -406,11 +414,16 @@ class ZimHostFragment : BaseFragment(), ZimHostCallbacks, ZimHostContract.View {
   override fun onDestroyView() {
     super.onDestroyView()
     activityZimHostBinding?.recyclerViewZimHost?.adapter = null
-    hotspotService?.registerCallBack(null)
+    unRegisterHotspotService()
     presenter.detachView()
     activityZimHostBinding = null
   }
 
+  private fun unRegisterHotspotService() {
+    hotspotService?.registerCallBack(null)
+    hotspotService = null
+  }
+
   // Advice user to turn on hotspot manually for API<26
   private fun startHotspotManuallyDialog() {
 
@@ -495,7 +508,9 @@ class ZimHostFragment : BaseFragment(), ZimHostCallbacks, ZimHostContract.View {
       createHotspotIntent(ACTION_START_SERVER).putStringArrayListExtra(
         SELECTED_ZIM_PATHS_KEY, selectedBooksPath
       ).putExtra(RESTART_SERVER, restartServer)
-    )
+    ).also {
+      isHotspotServiceRunning = true
+    }
   }
 
   override fun onIpAddressValid() {