feat(pferde-feature): introduce Pferde management module with screens, ViewModel, and domain models

- Added `pferde-feature` module for managing horses, including list, detail, and editing views.
- Implemented `MsMasterDetailLayout` for PferdeScreen, integrating `MsDataTable`, `MsFilterBar`, and `MsActionToolbar`.
- Defined domain models (`Pferd`, `Geschlecht`, `PferdeStatus`) with mock data support.
- Updated roadmap to mark `Pferde-Verwaltung (MVP)` as complete.
- Registered the new module in `settings.gradle.kts` and `meldestelle-desktop` build configuration.
- Added previews for Pferde and Reiter components to support IDE render.

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

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

@@ -7,6 +7,7 @@ import androidx.compose.foundation.layout.padding
 import androidx.compose.material3.Card
 import androidx.compose.material3.CardDefaults
 import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.unit.dp
@@ -40,3 +41,17 @@ fun MsCard(
     }
   }
 }
+
+// Preview für IDE (muss in jvmMain liegen um in IDEA gerendert zu werden,
+// oder hier bleiben als Dokumentation)
+@Composable
+fun MsCardPreviewContent() {
+  MaterialTheme {
+    Column(modifier = Modifier.padding(16.dp)) {
+      MsCard {
+        Text("Dies ist eine MsCard", style = MaterialTheme.typography.bodyMedium)
+        Text("Mit High-Density Content.", style = MaterialTheme.typography.bodySmall)
+      }
+    }
+  }
+}