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/shells/meldestelle-desktop/build.gradle.kts

@@ -38,6 +38,7 @@ kotlin {
       implementation(project(":frontend:features:reiter-feature"))
       implementation(project(":frontend:features:pferde-feature"))
       implementation(project(":frontend:features:billing-feature"))
+      implementation(project(":frontend:features:verein-feature"))
 
       // Compose Desktop
       implementation(compose.desktop.currentOs)