feat(verein-feature): add Vereinsverwaltung module with screens, ViewModel, and integration

- Introduced `verein-feature` module for managing Vereine, including list, detail, and editor views using `MsMasterDetailLayout`.
- Added new domain models (`Verein`, `VereinStatus`) and integrated mock data for development.
- Registered the new feature in `settings.gradle.kts` and `DesktopMainLayout.kt`, including breadcrumb navigation and entry point.
- Updated `VeranstaltungenUebersichtV2` to add Vereine as a quick-access KPI tile.
- Removed unnecessary logout functionality and adjusted the root navigation for consistency.

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

frontend/features/veranstaltung-feature/src/jvmMain/kotlin/at/mocode/veranstaltung/feature/presentation/AdminUebersichtScreen.kt

@@ -1,6 +1,7 @@
 package at.mocode.veranstaltung.feature.presentation
 
 import androidx.compose.foundation.BorderStroke
+import androidx.compose.foundation.clickable
 import androidx.compose.foundation.layout.*
 import androidx.compose.foundation.lazy.LazyColumn
 import androidx.compose.foundation.lazy.items
@@ -9,8 +10,8 @@ import androidx.compose.material.icons.filled.Add
 import androidx.compose.material.icons.filled.Delete
 import androidx.compose.material3.*
 import androidx.compose.runtime.Composable
-import androidx.compose.runtime.remember
 import androidx.compose.runtime.mutableStateListOf
+import androidx.compose.runtime.remember
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.Color
@@ -39,6 +40,7 @@ fun AdminUebersichtScreen(
   onVeranstalterAuswahl: () -> Unit,
   onVeranstaltungOeffnen: (Long) -> Unit,
   onPingService: () -> Unit = {},
+  onVereineOeffnen: () -> Unit = {},
 ) {
   // Placeholder-Daten für die UI-Struktur (sichtbar als Cards)
   val sample = listOf(
@@ -66,6 +68,7 @@ fun AdminUebersichtScreen(
       inVorbereitung = 0,
       gesamt = 0,
       archiv = 0,
+      onVereineClick = onVereineOeffnen
     )
 
     // Toolbar
@@ -155,6 +158,7 @@ private fun KpiKachelRow(
   inVorbereitung: Int,
   gesamt: Int,
   archiv: Int,
+  onVereineClick: () -> Unit = {},
 ) {
   Row(
     modifier = Modifier
@@ -175,10 +179,10 @@ private fun KpiKachelRow(
       modifier = Modifier.weight(1f),
     )
     KpiKachel(
-      label = "GESAMT",
-      wert = gesamt.toString(),
+      label = "VEREINE",
+      wert = "4", // Mock
       akzentFarbe = Color(0xFF6B7280),
-      modifier = Modifier.weight(1f),
+      modifier = Modifier.weight(1f).clickable { onVereineClick() },
     )
     KpiKachel(
       label = "ARCHIV",