Refactor envelope and history query structures

- Removed `Sender` parameter and properties from `EnvelopeQuery`.
- Deleted `SenderQuery` class entirely.
- Cleaned up `HistoryQuery` by removing unused `using` directives and `ReferenceType` logic.
- Added `Related` parameter to `ReadHistoryQuery` for reference type indication.
- Updated `ReferenceType` enum in `Constants.vb` to use explicit integer values.
- Modified `HistoryController` to utilize the new `Related` property for determining sender/receiver inclusion.

EnvelopeGenerator.Application/Envelopes/EnvelopeQuery.cs

@@ -6,27 +6,11 @@ namespace EnvelopeGenerator.Application.Envelopes;
 /// Repräsentiert eine Abfrage für Umschläge.
 /// </summary>
 /// <param name="Id">Die eindeutige Kennung des Umschlags.</param>
-/// <param name="Sender">Absender des Schreibens</param>
 /// <param name="Status">Der Status des Umschlags.</param>
 /// <param name="Uuid">Die universell eindeutige Kennung des Umschlags.</param>
 public record EnvelopeQuery(
     int? Id = null,
-    SenderQuery? Sender = null,
     int? Status = null,
     string? Uuid = null) : IRequest
 {
-    /// <summary>
-    /// Die eindeutige Kennung des Benutzers.
-    /// </summary>
-    public int? SenderId => Sender?.Id;
-
-    /// <summary>
-    /// Der Benutzername des Absenders.
-    /// </summary>
-    public string? SenderUsername => Sender?.Username;
-
-    /// <summary>
-    /// Die E-Mail-Adresse des Benutzers.
-    /// </summary>
-    public string? SenderEmail => Sender?.Username;
 };

EnvelopeGenerator.Application/Envelopes/SenderQuery.cs

@@ -1,11 +0,0 @@
-namespace EnvelopeGenerator.Application.Envelopes;
-
-/// <summary>
-/// Repräsentiert eine Abfrage für einen Absender.
-/// </summary>
-/// <param name="Id">Die eindeutige Kennung des Absenders.</param>
-/// <param name="Username">Der Benutzername des Absenders.</param>
-/// <param name="Email">Die E-Mail-Adresse des Absenders.</param>
-public record SenderQuery(int? Id = null, string? Username = null, string? Email = null)
-{
-}