Improved the creation of SpellingsDB on the IO thread.

* Fixed a native crash that occurred when the `SpellingsDB` creation was incomplete and the user closed the application. In such cases, a temporary folder (.tmp) remained, causing a `DatabaseCreateError` during the next initialization.
* Improved the font of "Do you mean:" text so that it could be show different from our suggestion items.

Author: MohitMaliDeveloper

core/src/main/java/org/kiwix/kiwixmobile/core/reader/ZimFileReader.kt

@@ -63,8 +63,6 @@ class ZimFileReader constructor(
   val jniKiwixReader: Archive,
   private val searcher: SuggestionSearcher
 ) {
-  private val spellingsDBCreationMutex = Mutex()
-
   interface Factory {
     suspend fun create(
       zimReaderSource: ZimReaderSource,
@@ -468,6 +466,8 @@ class ZimFileReader constructor(
     }
 
   companion object {
+    private val spellingsDBCreationMutex = Mutex()
+
     /*
      * these uris aren't actually nullable but unit tests fail to compile as
      * Uri.parse returns null without android dependencies loaded

core/src/main/java/org/kiwix/kiwixmobile/core/search/SearchScreen.kt

@@ -59,6 +59,7 @@ import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.semantics.contentDescription
 import androidx.compose.ui.semantics.semantics
 import androidx.compose.ui.semantics.testTag
+import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.text.style.TextOverflow.Companion.Ellipsis
 import org.kiwix.kiwixmobile.core.R
@@ -196,6 +197,7 @@ private fun LazyListScope.spellingCorrectionHeader() {
     Text(
       text = stringResource(R.string.do_you_mean),
       fontSize = SEARCH_ITEM_TEXT_SIZE,
+      fontWeight = FontWeight.Companion.W700,
       color = MaterialTheme.colorScheme.onBackground,
       modifier = Modifier
         .fillMaxWidth()

core/src/main/java/org/kiwix/kiwixmobile/core/utils/files/FileUtils.kt

@@ -68,9 +68,20 @@ object FileUtils {
     } else {
       context.cacheDir
     }
-    return File(baseCacheDir, SPELLING_DB_CACHED_DIRECTORY).apply {
+
+    val spellingDBCacheDir = File(baseCacheDir, SPELLING_DB_CACHED_DIRECTORY).apply {
       if (!exists()) mkdirs()
     }
+
+    // Clean up any incomplete `.tmp` folders inside the spelling DB directory
+    spellingDBCacheDir.listFiles()?.forEach { file ->
+      if (file.isDirectory && file.name.endsWith(".tmp")) {
+        file.deleteRecursively()
+        Log.w(TAG_KIWIX, "Deleted incomplete SpellingsDB folder: ${file.absolutePath}")
+      }
+    }
+
+    return spellingDBCacheDir
   }
 
   @JvmStatic