feat(CUB-8): Create background service for Moonraker mapping

backend/Domain/Interfaces/IMoonrakerPrinterSyncService.cs

@@ -0,0 +1,20 @@
+using Extrudex.Domain.DTOs.Moonraker;
+
+namespace Extrudex.Domain.Interfaces;
+
+/// <summary>
+/// Service interface for syncing Moonraker printer data into the Extrudex database.
+/// Handles periodic polling of printer status and mapping print job history
+/// to PrintJob and FilamentUsage entities.
+/// </summary>
+public interface IMoonrakerPrinterSyncService
+{
+    /// <summary>
+    /// Performs a single sync cycle: queries all active Moonraker printers,
+    /// fetches their current status and print job history, and persists
+    /// updates to the database.
+    /// </summary>
+    /// <param name="cancellationToken">Cancellation token for graceful shutdown.</param>
+    /// <returns>The number of printers successfully synced.</returns>
+    Task<int> SyncAllAsync(CancellationToken cancellationToken = default);
+}