style: simplify db declaration

app/src/main/java/ru/sweetbread/unn/ui/layout/MainActivity.kt

@@ -38,6 +38,7 @@ import ru.sweetbread.unn.db.AppDatabase
 import ru.sweetbread.unn.ui.composes.Blogposts
 import ru.sweetbread.unn.ui.composes.Schedule
 import ru.sweetbread.unn.ui.theme.UNNTheme
+import splitties.arch.room.roomDb
 import splitties.toast.toast
 
 val client = HttpClient(Android) {
@@ -62,18 +63,13 @@ val client = HttpClient(Android) {
     }
 }
 
-lateinit var db: AppDatabase
+val db = roomDb<AppDatabase>(name = "database")
 
 class MainActivity : ComponentActivity() {
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
 
-        db = Room.databaseBuilder(
-            applicationContext,
-            AppDatabase::class.java, "database"
-        ).build()
-
         setContent {
             UNNTheme {
                 Surface(modifier = Modifier.fillMaxSize(), color = MaterialTheme.colorScheme.background) {