Make ActionId a required field across DTOs and entities

Updated the `RecActionDto`, `RecAction`, and `InvokeRecActionCommandHandler` to enforce `ActionId` as a required field. This change improves data integrity by removing nullable `ActionId` properties and eliminates the need for null checks or null-forgiveness operators.

src/ReC.Application/Common/Dto/RecActionDto.cs

@@ -2,7 +2,7 @@
 
 public record RecActionDto
 {
-    public long? ActionId { get; init; }
+    public required long ActionId { get; init; }
 
     public long? ProfileId { get; init; }