refactor(core): integrate localDbModule into DI setup and update SyncManager to use named apiClient

Added `localDbModule` to the Koin initialization list in `main.kt` for enhanced modularity. Updated `SyncManager` DI in `SyncModule.kt` to use the named `apiClient` for better dependency resolution. Improved code maintainability.

frontend/core/sync/src/commonMain/kotlin/at/mocode/frontend/core/sync/di/SyncModule.kt

@@ -1,12 +1,13 @@
 package at.mocode.frontend.core.sync.di
 
 import at.mocode.frontend.core.sync.SyncManager
+import org.koin.core.qualifier.named
 import org.koin.dsl.module
 
 /**
  * Zentrales Koin-Modul für den Sync-Core.
  */
 val syncModule = module {
-  // Provides a singleton instance of SyncManager, using the globally provided HttpClient.
-  single { SyncManager(get()) }
+  // Provides a singleton instance of SyncManager, using the authenticated 'apiClient'.
+  single { SyncManager(get(named("apiClient"))) }
 }