scanner improvements (#1122)

* optimize periodic scanning

* set scanner process priority

* update dependencies

ErsatzTV.Core/Errors/ScanIsNotRequired.cs

@@ -0,0 +1,8 @@
+namespace ErsatzTV.Core.Errors;
+
+public class ScanIsNotRequired : BaseError
+{
+    public ScanIsNotRequired() : base("Scan is not required")
+    {
+    }
+}