Add InsertResultCommandValidator with validation rules

Introduce InsertResultCommandValidator using FluentValidation to enforce required and value constraints on ActionId and References.BatchId properties, including custom error messages.

src/ReC.Application/Common/Validations/InsertResultCommandValidator.cs

@@ -0,0 +1,21 @@
+using FluentValidation;
+using ReC.Application.Results.Commands;
+
+namespace ReC.Application.Common.Validations;
+
+public class InsertResultCommandValidator : AbstractValidator<InsertResultCommand>
+{
+    public InsertResultCommandValidator()
+    {
+        RuleFor(x => x.ActionId)
+            .NotNull()
+            .WithMessage("ActionId is required.")
+            .GreaterThan(0L)
+            .When(x => x.ActionId.HasValue)
+            .WithMessage("ActionId must be greater than 0.");
+
+        RuleFor(x => x.References.BatchId)
+            .NotEmpty()
+            .WithMessage("BatchId is required.");
+    }
+}