implement category preselection in StartExerciseScreen and update navigation logic from CategoryDetailScreen

app/build.gradle.kts

@@ -126,6 +126,7 @@ dependencies {
     implementation(libs.androidx.room.runtime) // ADDED: Explicitly add runtime
     implementation(libs.androidx.room.ktx)
     implementation(libs.core.ktx)
+    implementation(libs.androidx.compose.runtime)
     ksp(libs.room.compiler)
 
     // Networking

app/src/main/java/eu/gaudian/translator/view/Navigation.kt

@@ -154,8 +154,22 @@ fun AppNavHost(
             NewWordReviewScreen(navController = navController)
         }
 
-        composable(NavigationRoutes.START_EXERCISE) {
-            StartExerciseScreen(navController = navController)
+        composable(
+            route = "${NavigationRoutes.START_EXERCISE}?categoryId={categoryId}",
+            arguments = listOf(
+                navArgument("categoryId") {
+                    type = NavType.StringType
+                    nullable = true
+                    defaultValue = null
+                }
+            )
+        ) { backStackEntry ->
+            val categoryIdString = backStackEntry.arguments?.getString("categoryId")
+            val categoryId = categoryIdString?.toIntOrNull()
+            StartExerciseScreen(
+                navController = navController,
+                preselectedCategoryId = categoryId
+            )
         }
 
         // Define all other navigation graphs at the same top level.

app/src/main/java/eu/gaudian/translator/view/exercises/StartExerciseScreen.kt

@@ -35,6 +35,7 @@ import androidx.compose.material3.Surface
 import androidx.compose.material3.Text
 import androidx.compose.material3.rememberModalBottomSheetState
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableIntStateOf
@@ -76,17 +77,30 @@ import kotlinx.coroutines.launch
 @Composable
 fun StartExerciseScreen(
     navController: NavHostController,
+    preselectedCategoryId: Int? = null,
     modifier: Modifier = Modifier
 ) {
     val activity = androidx.compose.ui.platform.LocalContext.current.findActivity()
     val vocabularyViewModel: VocabularyViewModel = hiltViewModel(viewModelStoreOwner = activity)
+    val categoryViewModel: CategoryViewModel = hiltViewModel(viewModelStoreOwner = activity)
     val exerciseViewModel: VocabularyExerciseViewModel = hiltViewModel(viewModelStoreOwner = activity)
 
     val exerciseConfig by exerciseViewModel.pendingExerciseConfig.collectAsState()
+    val allCategories by categoryViewModel.categories.collectAsState(initial = emptyList())
     var selectedLanguagePairs by remember { mutableStateOf<List<Pair<Language, Language>>>(emptyList()) }
     var selectedCategories by remember { mutableStateOf<List<VocabularyCategory>>(emptyList()) }
     var selectedStages by remember { mutableStateOf<List<VocabularyStage>>(emptyList()) }
 
+    // Initialize preselected category
+    LaunchedEffect(allCategories, preselectedCategoryId) {
+        if (preselectedCategoryId != null) {
+            val category = allCategories.find { it.id == preselectedCategoryId }
+            if (category != null && category !in selectedCategories) {
+                selectedCategories = listOf(category)
+            }
+        }
+    }
+
     var selectedOriginLanguage by remember { mutableStateOf<Language?>(null) }
     var selectedTargetLanguage by remember { mutableStateOf<Language?>(null) }
     val isDirectionPreferenceSet = selectedOriginLanguage != null || selectedTargetLanguage != null

app/src/main/java/eu/gaudian/translator/view/vocabulary/CategoryDetailScreen.kt

@@ -255,9 +255,7 @@ fun CategoryDetailScreen(
                         subtitle = subtitle,
                         categoryProgress = categoryProgress,
                         onStartExerciseClick = {
-                            val categories = listOf(category)
-                            val categoryIds = categories.joinToString(",") { it?.id.toString() }
-                            navController.navigate("vocabulary_exercise/false?categories=$categoryIds")
+                            navController.navigate("start_exercise?categoryId=$categoryId")
                         },
                         onEditClick = {
                             categoryViewModel.setShowEditCategoryDialog(true, categoryId)