refactor(ping-service): remove CORS configuration from code, restructure modules, and update Gradle dependencies

Migrated CORS settings from code to `application.yaml` for better separation of concerns. Integrated `ping-api` into the new `contracts` module for improved modularity. Updated Gradle scripts and dependencies accordingly to reflect the new project structure.

contracts/ping-api/src/commonMain/kotlin/at/mocode/ping/api/PingApi.kt

@@ -0,0 +1,7 @@
+package at.mocode.ping.api
+
+interface PingApi {
+    suspend fun simplePing(): PingResponse
+    suspend fun enhancedPing(simulate: Boolean = false): EnhancedPingResponse
+    suspend fun healthCheck(): HealthResponse
+}

contracts/ping-api/src/commonMain/kotlin/at/mocode/ping/api/PingData.kt

@@ -0,0 +1,23 @@
+package at.mocode.ping.api
+
+import kotlinx.serialization.Serializable
+
+@Serializable
+data class PingResponse(val status: String, val timestamp: String, val service: String)
+
+@Serializable
+data class EnhancedPingResponse(
+    val status: String,
+    val timestamp: String,
+    val service: String,
+    val circuitBreakerState: String,
+    val responseTime: Long
+)
+
+@Serializable
+data class HealthResponse(
+    val status: String,
+    val timestamp: String,
+    val service: String,
+    val healthy: Boolean
+)