Restructure solution layout by module

src/Scanner/StellaOps.Scanner.Worker/Processing/NullScanJobSource.cs

@@ -0,0 +1,26 @@
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.Extensions.Logging;
+
+namespace StellaOps.Scanner.Worker.Processing;
+
+public sealed class NullScanJobSource : IScanJobSource
+{
+    private readonly ILogger<NullScanJobSource> _logger;
+    private int _logged;
+
+    public NullScanJobSource(ILogger<NullScanJobSource> logger)
+    {
+        _logger = logger;
+    }
+
+    public Task<IScanJobLease?> TryAcquireAsync(CancellationToken cancellationToken)
+    {
+        if (Interlocked.Exchange(ref _logged, 1) == 0)
+        {
+            _logger.LogWarning("No queue provider registered. Scanner worker will idle until a queue adapter is configured.");
+        }
+
+        return Task.FromResult<IScanJobLease?>(null);
+    }
+}