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/features/zns-import-feature/build.gradle.kts

@@ -0,0 +1,28 @@
+/**
+ * Feature-Modul: ZNS-Stammdaten-Import (Desktop-only)
+ * Kapselt ViewModel, State und API-Kommunikation für den ZNS-Import.
+ */
+plugins {
+  alias(libs.plugins.kotlinMultiplatform)
+  alias(libs.plugins.composeCompiler)
+}
+group = "at.mocode.clients"
+version = "1.0.0"
+
+kotlin {
+  jvm()
+  sourceSets {
+    jvmMain.dependencies {
+      implementation(projects.frontend.core.network)
+      implementation(projects.frontend.core.auth)
+      implementation(libs.bundles.kmp.common)
+      implementation(libs.koin.core)
+      implementation(libs.ktor.client.core)
+      implementation(libs.ktor.client.contentNegotiation)
+      implementation(libs.ktor.client.serialization.kotlinx.json)
+      implementation(libs.androidx.lifecycle.viewmodelCompose)
+      implementation(libs.kotlinx.coroutines.core)
+      implementation(libs.kotlinx.serialization.json)
+    }
+  }
+}