Refactor namespaces and simplify DTOs

Updated namespaces to align with the new DigitalData.Core structure, replacing `DigitalData.Core.Abstractions` with `DigitalData.Core.Application.Interfaces` and `DigitalData.Core.Client.Interface`. Removed the `IUnique<int>` interface from several DTOs, simplifying their design and altering the handling of entity identification. Updated project files to reflect new dependency versions for improved compatibility and features. Cleaned up using directives to remove obsolete references, enhancing code maintainability.

EnvelopeGenerator.Application/DTOs/ConfigDto.cs

@@ -1,7 +1,4 @@
-using DigitalData.Core.Abstractions;
-using Microsoft.AspNetCore.Mvc;
-using System.ComponentModel.DataAnnotations.Schema;
-using System.Text.Json.Serialization;
+using Microsoft.AspNetCore.Mvc;
 
 namespace EnvelopeGenerator.Application.DTOs;
 
@@ -9,7 +6,7 @@ namespace EnvelopeGenerator.Application.DTOs;
 /// Data Transfer Object representing configuration settings.
 /// </summary>
 [ApiExplorerSettings(IgnoreApi = true)]
-public class ConfigDto : IUnique<int>
+public class ConfigDto
 {
     /// <summary>
     /// Gets or sets the path to the document.
@@ -35,13 +32,4 @@ public class ConfigDto : IUnique<int>
     /// Gets or sets the path where exports will be saved.
     /// </summary>
     public string ExportPath { get; set; }
-
-    /// <summary>
-    /// Gets the ID of the configuration.
-    /// This DTO represents a single row in the database and does not support an ID.
-    /// </summary>
-    [NotMapped]
-    [JsonIgnore]
-    [Obsolete("Configuration does not have an ID; it represents a single table in the database.")]
-    public int Id => throw new InvalidOperationException("This configuration does not support an ID as it represents a single row in the database.");
 }