Fix UI freeze after migration

Fixes #938

app/src/main/java/mihon/core/migration/MigrationStrategyFactory.kt

@@ -6,15 +6,13 @@ class MigrationStrategyFactory(
 ) {
 
     fun create(old: Int, new: Int): MigrationStrategy {
-        val versions = (old + 1)..new
         val strategy = when {
             old == 0 -> InitialMigrationStrategy(
                 strategy = DefaultMigrationStrategy(factory, migrationCompletedListener, Migrator.scope),
             )
-
             old >= new -> NoopMigrationStrategy(false)
             else -> VersionRangeMigrationStrategy(
-                versions = versions,
+                versions = (old + 1)..new,
                 strategy = DefaultMigrationStrategy(factory, migrationCompletedListener, Migrator.scope),
             )
         }

app/src/main/java/mihon/core/migration/Migrator.kt

@@ -10,7 +10,7 @@ import kotlinx.coroutines.runBlocking
 object Migrator {
 
     private var result: Deferred<Boolean>? = null
-    val scope = CoroutineScope(Dispatchers.Main + Job())
+    val scope = CoroutineScope(Dispatchers.IO + Job())
 
     fun initialize(
         old: Int,