feat(CUB-39): create background job for filament usage sync

backend/Program.cs

@@ -1,7 +1,9 @@
 using System.Reflection;
 using Extrudex.API.Filters;
 using Extrudex.API.Hubs;
+using Extrudex.API.Jobs;
 using Extrudex.Domain.Interfaces;
+using Extrudex.Infrastructure.Configuration;
 using Extrudex.Infrastructure.Data;
 using Extrudex.Infrastructure.Services;
 using FluentValidation;
@@ -77,6 +79,16 @@ builder.Services.AddCors(options =>
 // ── SignalR (real-time printer updates) ────────────────────
 builder.Services.AddSignalR();
 
+// ── Filament Usage Sync (Background Job) ──────────────────
+builder.Services.Configure<FilamentUsageSyncOptions>(
+    builder.Configuration.GetSection(FilamentUsageSyncOptions.SectionName));
+builder.Services.AddHttpClient<IMoonrakerClient, MoonrakerClient>(client =>
+{
+    client.DefaultRequestHeaders.Add("User-Agent", "Extrudex/1.0");
+});
+builder.Services.AddScoped<IFilamentUsageSyncService, FilamentUsageSyncService>();
+builder.Services.AddHostedService<FilamentUsageSyncJob>();
+
 // ── Health Checks ───────────────────────────────────────────
 builder.Services.AddHealthChecks()
     .AddNpgSql(connectionString);