chore: remove unused meldestelle-portal module

- Deleted obsolete `meldestelle-portal` module, including all associated screens, configurations, tests, and assets.
- Includes removal of Compose multiplatform dependencies in `build.gradle.kts`.
- Cleaned up redundant files such as `AppPreview`, `AuthStatusScreen`, `DashboardScreen`, and associated core implementations.
- Streamlined module references in `settings.gradle.kts`.

Signed-off-by: Stefan Mogeritsch <stefan.mo.co@gmail.com>

frontend/core/navigation/src/commonMain/kotlin/at/mocode/frontend/core/navigation/AppScreen.kt

@@ -28,8 +28,13 @@ sealed class AppScreen(val route: String) {
   data object Funktionaere : AppScreen("/funktionaere")
   data object Meisterschaften : AppScreen("/meisterschaften")
   data object Cups : AppScreen("/cups")
+  data object StammdatenImport : AppScreen("/stammdaten/import")
 
   companion object {
+    private val VERANSTALTUNG_DETAIL = Regex("/veranstaltung/(\\d+)$")
+    private val TURNIER_DETAIL = Regex("/veranstaltung/(\\d+)/turnier/(\\d+)$")
+    private val TURNIER_NEU = Regex("/veranstaltung/(\\d+)/turnier/neu$")
+
     fun fromRoute(route: String): AppScreen {
       return when (route) {
         Routes.HOME -> Landing
@@ -49,7 +54,19 @@ sealed class AppScreen(val route: String) {
         "/funktionaere" -> Funktionaere
         "/meisterschaften" -> Meisterschaften
         "/cups" -> Cups
-        else -> Landing // Default fallback
+        "/stammdaten/import" -> StammdatenImport
+        else -> {
+          TURNIER_DETAIL.matchEntire(route)?.destructured?.let { (vId, tId) ->
+            return TurnierDetail(vId.toLong(), tId.toLong())
+          }
+          TURNIER_NEU.matchEntire(route)?.destructured?.let { (vId) ->
+            return TurnierNeu(vId.toLong())
+          }
+          VERANSTALTUNG_DETAIL.matchEntire(route)?.destructured?.let { (id) ->
+            return VeranstaltungDetail(id.toLong())
+          }
+          Landing // Default fallback
+        }
       }
     }
   }

frontend/core/navigation/src/commonMain/kotlin/at/mocode/frontend/core/navigation/NavigationPort.kt

@@ -1,9 +1,18 @@
 package at.mocode.frontend.core.navigation
 
+import kotlinx.coroutines.flow.StateFlow
+
 /**
- * Minimal navigation abstraction used by core navigation components.
- * The actual implementation lives in shells/apps and delegates to the app's router.
+ * Navigations-Abstraktion für alle Shells.
+ * Die konkrete Implementierung liegt in der jeweiligen Shell (z.B. DesktopNavigationPort).
  */
 interface NavigationPort {
+  /** Aktuell angezeigter Screen als reaktiver State. */
+  val currentScreen: StateFlow<AppScreen>
+
+  /** Navigation via Route-String (z.B. für Deep-Links). */
   fun navigateTo(route: String)
+
+  /** Typsichere Navigation direkt via AppScreen-Objekt. */
+  fun navigateToScreen(screen: AppScreen)
 }