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- Removed deprecated `NotificationCard` component due to dependency on an outdated presentation layer.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/core/design-system/src/commonMain/kotlin/at/mocode/frontend/core/designsystem/components/AppHeader.kt

@@ -35,7 +35,7 @@ fun AppHeader(
 
       // Authentication buttons
       if (isAuthenticated) {
-        // Show username with admin indicator if user has delete permissions
+        // Show username with admin indicator if user has deleted permissions
         username?.let { user ->
           val isAdmin = userPermissions.any { it.contains("DELETE") }
           Text(
@@ -55,7 +55,7 @@ fun AppHeader(
           }
         }
       } else {
-        // Show login button
+        // Show the login button
         onNavigateToLogin?.let { loginAction ->
           TextButton(
             onClick = loginAction

frontend/core/design-system/src/commonMain/kotlin/at/mocode/frontend/core/designsystem/components/NotificationCard.kt

@@ -1,5 +0,0 @@
-package at.mocode.frontend.core.designsystem.components
-
-// Legacy notification components removed due to dependency on old presentation layer.
-// Intentionally left empty as part of cleanup. You can safely delete this file
-// if no modules import it anymore.

frontend/core/design-system/src/commonMain/kotlin/at/mocode/frontend/core/designsystem/theme/AppTheme.kt

@@ -14,7 +14,7 @@ import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.unit.sp
 
 // --- 1. Farben (Palette) ---
-// Wir definieren eine professionelle, kontrastreiche Palette.
+// wir definieren eine professionelle, kontrastreiche Palette.
 // Blau steht für Aktion/Information, Grau für Struktur.
 
 private val LightColorScheme = lightColorScheme(