chore(frontend): refactor navigation and DI setup, remove unused shared module

- Replaced `initKoin` with `startKoin` for DI initialization consistency across platforms.
- Introduced `StateNavigationPort` with `StateFlow` to streamline navigation state management.
- Migrated `AppScreen` to sealed class with route mapping for better navigation handling.
- Deleted unused `frontend/shared` module and removed related dependencies from build files.
- Cleaned up legacy navigation and Redux-related code, aligning with MVVM architecture.

backend/infrastructure/cache/cache-api/build.gradle.kts

@@ -1,5 +1,5 @@
 // Dieses Modul definiert die provider-agnostische Caching-API.
-// Es enthält nur Interfaces (z.B. `CacheService`) und Datenmodelle,
+// Es enthält nur Interfaces (z. B. `CacheService`) und Datenmodelle,
 // aber keine konkrete Implementierung.
 plugins {
     alias(libs.plugins.kotlinJvm)