refactor(frontend, build): update PingViewModel initialization, resolve view model via Koin, and clean yarn dependencies

Injected `PingViewModel` via Koin to align with dependency injection best practices. Suppressed Gradle deprecation warnings and added the `frontend.core.sync` dependency. Cleaned up outdated packages in `yarn.lock`.

frontend/core/sync/build.gradle.kts

@@ -0,0 +1,33 @@
+plugins {
+  alias(libs.plugins.kotlinMultiplatform)
+  alias(libs.plugins.kotlinSerialization)
+}
+
+kotlin {
+  // Targets are configured centrally in the shells/feature modules; here we just provide common code.
+  jvm()
+  js(IR) {
+    browser()
+  }
+
+  sourceSets {
+    commonMain.dependencies {
+      implementation(projects.core.coreDomain)
+
+      // Networking
+      implementation(libs.ktor.client.core)
+      implementation(libs.ktor.client.contentNegotiation)
+      implementation(libs.ktor.client.serialization.kotlinx.json)
+
+      // Serialization
+      implementation(libs.kotlinx.serialization.json)
+
+      // DI
+      implementation(libs.koin.core)
+    }
+
+    commonTest.dependencies {
+      implementation(libs.kotlin.test)
+    }
+  }
+}

frontend/core/sync/src/commonMain/kotlin/at/mocode/frontend/core/sync/SyncCore.kt

@@ -0,0 +1,54 @@
+package at.mocode.frontend.core.sync
+
+import at.mocode.core.sync.Syncable
+import io.ktor.client.HttpClient
+import io.ktor.client.call.body
+import io.ktor.client.request.get
+import io.ktor.client.request.parameter
+
+/**
+ * Minimaler Repository-Contract für Delta-Sync.
+ */
+interface SyncableRepository<T : Syncable> {
+  /**
+   * Cursor für Delta-Sync.
+   *
+   * Konvention: UUIDv7 als String (Backend kann `>` vergleichen) oder ein kompatibler Cursor.
+   *
+   * @return letzter bekannter Cursor lokal oder `null`, wenn noch keine Daten existieren.
+   */
+  suspend fun getLatestSince(): String?
+
+  /** Insert oder Update (Upsert) der übergebenen Items. */
+  suspend fun upsert(items: List<T>)
+}
+
+/**
+ * Generischer Sync-Manager.
+ *
+ * Konvention Backend:
+ * - GET `/api/{entity-plural}/sync?since={timestamp}`
+ * - Response: `List<T>`
+ */
+class SyncManager(
+  val ktorClient: HttpClient
+) {
+
+  suspend inline fun <reified T : Syncable> performSync(
+    repository: SyncableRepository<T>,
+    endpointPath: String
+  ) {
+    val since = repository.getLatestSince()
+
+    val remoteItems: List<T> = ktorClient
+      .get(endpointPath) {
+        // `since` optional
+        if (since != null) parameter("since", since)
+      }
+      .body()
+
+    if (remoteItems.isNotEmpty()) {
+      repository.upsert(remoteItems)
+    }
+  }
+}

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

@@ -0,0 +1,12 @@
+package at.mocode.frontend.core.sync.di
+
+import at.mocode.frontend.core.sync.SyncManager
+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()) }
+}