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.

frontend/core/design-system/build.gradle.kts

@@ -24,8 +24,6 @@ kotlin {
 
   sourceSets {
     commonMain.dependencies {
-      // Shared module dependency
-      implementation(projects.frontend.shared)
 
       // Compose dependencies
       implementation(compose.runtime)