chore(frontend): cleanup legacy code and improve localization consistency

- Removed deprecated `NotificationCard` component due to dependency on an outdated presentation layer.
- Translated comments and documentation to German for improved localization across `core.auth`, `ping-feature`, and `network`.
- Standardized comment formatting, improved doc clarity, and ensured consistent API documentation in all modules.

frontend/features/ping-feature/src/commonMain/kotlin/at/mocode/ping/feature/data/PingApiKoinClient.kt

@@ -10,7 +10,8 @@ import io.ktor.client.call.body
 import io.ktor.client.request.get
 
 /**
- * PingApi implementation that uses a provided HttpClient (e.g., DI-provided "apiClient").
+ * PingApi-Implementierung, die einen bereitgestellten HttpClient verwendet (z. B. den per Dependency Injection
+ * bereitgestellten "apiClient").
  */
 class PingApiKoinClient(private val client: HttpClient) : PingApi {
 

frontend/features/ping-feature/src/commonMain/kotlin/at/mocode/ping/feature/data/PingEventRepositoryImpl.kt

@@ -5,21 +5,24 @@ import at.mocode.frontend.core.sync.SyncableRepository
 import at.mocode.ping.api.PingEvent
 import app.cash.sqldelight.async.coroutines.awaitAsOneOrNull
 
-// ARCH-BLUEPRINT: This repository implements the generic SyncableRepository
-// for a specific entity, bridging the gap between the sync core and the local database.
+/**
+ ** ARCH-BLUEPRINT: Dieses Repository implementiert das generische Syncable Repository
+ ** für eine bestimmte Entität und überbrückt so die Lücke zwischen dem Sync-Core und der
+ ** lokalen Datenbank.
+ */
 class PingEventRepositoryImpl(
   private val db: AppDatabase
 ) : SyncableRepository<PingEvent> {
 
-  // The `since` parameter for our sync is the ID of the last event, not a timestamp.
+  // Der `since`-Parameter für unsere Synchronisierung ist die ID des letzten Ereignisses, kein Zeitstempel.
   override suspend fun getLatestSince(): String? {
-      println("PingEventRepositoryImpl: getLatestSince called - using corrected async implementation")
-      // FIX: Use .awaitAsOneOrNull() for async drivers instead of the blocking .executeAsOneOrNull()
-      return db.appDatabaseQueries.selectLatestPingEventId().awaitAsOneOrNull()
+    println("PingEventRepositoryImpl: getLatestSince called - using corrected async implementation")
+    // FIX: Verwenden Sie .awaitAsOneOrNull() für asynchrone Treiber anstelle des blockierenden .executeAsOneOrNull().
+    return db.appDatabaseQueries.selectLatestPingEventId().awaitAsOneOrNull()
   }
 
   override suspend fun upsert(items: List<PingEvent>) {
-    // Always perform bulk operations within a transaction.
+    // Führen Sie Massenoperationen immer innerhalb einer Transaktion durch.
     db.transaction {
       items.forEach { event ->
         db.appDatabaseQueries.upsertPingEvent(

frontend/features/ping-feature/src/commonMain/kotlin/at/mocode/ping/feature/di/PingFeatureModule.kt

@@ -11,19 +11,18 @@ import org.koin.core.qualifier.named
 import org.koin.dsl.module
 
 /**
- * Consolidated Koin module for the Ping Feature (Clean Architecture).
- * Replaces the old 'clients.pingfeature' module.
+ * Konsolidiertes Koin-Modul für die Ping-Funktion (Clean Architecture).
  */
 val pingFeatureModule = module {
   // 1. API Client (Data Layer)
-  // Uses the shared authenticated 'apiClient' from Core Network
+  // Verwendet den gemeinsam genutzten, authentifizierten „apiClient“ aus dem Kernnetzwerk.
   single<PingApi> { PingApiKoinClient(get(named("apiClient"))) }
 
   // 2. Repository (Data Layer)
   single { PingEventRepositoryImpl(get<AppDatabase>()) }
 
   // 3. Domain Service (Domain Layer)
-  // Wraps SyncManager and Repository to decouple ViewModel from SyncManager implementation details
+  // Wraps SyncManager und Repository, um ViewModel von den Implementierungsdetails von SyncManager zu entkoppeln.
   single<PingSyncService> {
     PingSyncServiceImpl(
       syncManager = get(),
@@ -32,7 +31,7 @@ val pingFeatureModule = module {
   }
 
   // 4. ViewModel (Presentation Layer)
-  // Injects API and Domain Service
+  // Injects API und Domain Service
   factory {
     PingViewModel(
       apiClient = get(),

frontend/features/ping-feature/src/commonMain/kotlin/at/mocode/ping/feature/domain/PingSyncService.kt

@@ -5,14 +5,14 @@ import at.mocode.frontend.core.sync.SyncableRepository
 import at.mocode.ping.api.PingEvent
 
 /**
- * Interface for the Ping Sync Service to allow easier testing and decoupling.
+ * Interface für den Ping-Sync-Dienst zur einfacheren Prüfung und Entkopplung.
  */
 interface PingSyncService {
   suspend fun syncPings()
 }
 
 /**
- * Implementation of PingSyncService using the generic SyncManager.
+ * Implementierung des PingSyncService unter Verwendung des generischen SyncManager.
  */
 class PingSyncServiceImpl(
   private val syncManager: SyncManager,

frontend/features/ping-feature/src/commonMain/kotlin/at/mocode/ping/feature/presentation/PingScreen.kt

@@ -19,8 +19,6 @@ import at.mocode.frontend.core.designsystem.components.DashboardCard
 import at.mocode.frontend.core.designsystem.components.DenseButton
 import at.mocode.frontend.core.designsystem.theme.Dimens
 
-// --- Refactored PingScreen using Design System ---
-
 @Composable
 fun PingScreen(
   viewModel: PingViewModel,

frontend/features/ping-feature/src/commonTest/kotlin/at/mocode/ping/feature/data/PingApiKoinClientTest.kt

@@ -15,7 +15,7 @@ import kotlin.test.assertEquals
 
 class PingApiKoinClientTest {
 
-  // Helper to create a testable client using the new DI-friendly implementation
+  // Hilfe zur Erstellung eines testbaren Clients mithilfe der neuen DI-freundlichen Implementierung
   private fun createTestClient(mockEngine: MockEngine): PingApiKoinClient {
     val client = HttpClient(mockEngine) {
       install(ContentNegotiation) {