RSVP options.

Wino.Core/Requests/Calendar/AcceptEventRequest.cs

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+using CommunityToolkit.Mvvm.Messaging;
+using Wino.Core.Domain.Entities.Calendar;
+using Wino.Core.Domain.Enums;
+using Wino.Core.Domain.Models.Requests;
+using Wino.Messaging.Client.Calendar;
+
+namespace Wino.Core.Requests.Calendar;
+
+/// <summary>
+/// Request to accept a calendar event invitation on the server.
+/// The calendar item status should be updated locally before queuing this request.
+/// </summary>
+public record AcceptEventRequest(CalendarItem Item, string ResponseMessage = null) : CalendarRequestBase(Item)
+{
+    private readonly CalendarItemStatus _previousStatus = Item.Status;
+
+    public override CalendarSynchronizerOperation Operation => CalendarSynchronizerOperation.AcceptEvent;
+
+    /// <summary>
+    /// After successful acceptance, we need to resync to get updated status.
+    /// </summary>
+    public override int ResynchronizationDelay => 2000;
+
+    public override void ApplyUIChanges()
+    {
+        // Update the item status locally
+        Item.Status = CalendarItemStatus.Accepted;
+        
+        // Notify UI that the event status was updated
+        WeakReferenceMessenger.Default.Send(new CalendarItemUpdated(Item));
+    }
+
+    public override void RevertUIChanges()
+    {
+        // If acceptance fails, revert to the previous status
+        Item.Status = _previousStatus;
+        WeakReferenceMessenger.Default.Send(new CalendarItemUpdated(Item));
+    }
+}

Wino.Core/Requests/Calendar/DeclineEventRequest.cs

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+using CommunityToolkit.Mvvm.Messaging;
+using Wino.Core.Domain.Entities.Calendar;
+using Wino.Core.Domain.Enums;
+using Wino.Core.Domain.Models.Requests;
+using Wino.Messaging.Client.Calendar;
+
+namespace Wino.Core.Requests.Calendar;
+
+/// <summary>
+/// Request to decline a calendar event invitation on the server.
+/// The calendar item status should be updated locally before queuing this request.
+/// </summary>
+public record DeclineEventRequest(CalendarItem Item, string ResponseMessage = null) : CalendarRequestBase(Item)
+{
+    private readonly CalendarItemStatus _previousStatus = Item.Status;
+
+    public override CalendarSynchronizerOperation Operation => CalendarSynchronizerOperation.DeclineEvent;
+
+    /// <summary>
+    /// After successful decline, we need to resync to get updated status.
+    /// </summary>
+    public override int ResynchronizationDelay => 2000;
+
+    public override void ApplyUIChanges()
+    {
+        // Update the item status locally
+        Item.Status = CalendarItemStatus.Cancelled;
+
+        // Notify UI that the event status was updated
+        WeakReferenceMessenger.Default.Send(new CalendarItemUpdated(Item));
+    }
+
+    public override void RevertUIChanges()
+    {
+        // If decline fails, revert to the previous status
+        Item.Status = _previousStatus;
+        WeakReferenceMessenger.Default.Send(new CalendarItemUpdated(Item));
+    }
+}

Wino.Core/Requests/Calendar/OutlookDeclineEventRequest.cs

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+using CommunityToolkit.Mvvm.Messaging;
+using Wino.Core.Domain.Entities.Calendar;
+using Wino.Core.Domain.Enums;
+using Wino.Core.Domain.Models.Requests;
+using Wino.Messaging.Client.Calendar;
+
+namespace Wino.Core.Requests.Calendar;
+
+/// <summary>
+/// Outlook-specific request to decline a calendar event invitation.
+/// In Outlook, declined events are removed from the calendar by the API after synchronization,
+/// so this request sends a delete notification to remove the event from the UI.
+/// </summary>
+public record OutlookDeclineEventRequest(CalendarItem Item, string ResponseMessage = null) : CalendarRequestBase(Item)
+{
+    private readonly CalendarItemStatus _previousStatus = Item.Status;
+
+    public override CalendarSynchronizerOperation Operation => CalendarSynchronizerOperation.DeclineEvent;
+
+    /// <summary>
+    /// After successful decline, we need to resync to confirm the event is removed.
+    /// </summary>
+    public override int ResynchronizationDelay => 2000;
+
+    public override void ApplyUIChanges()
+    {
+        // In Outlook, declined events are deleted from the calendar after sync
+        // Send deleted message to remove from UI immediately
+        WeakReferenceMessenger.Default.Send(new CalendarItemDeleted(Item));
+    }
+
+    public override void RevertUIChanges()
+    {
+        // If decline fails, restore the previous status and re-add the event
+        Item.Status = _previousStatus;
+        WeakReferenceMessenger.Default.Send(new CalendarItemAdded(Item));
+    }
+}

Wino.Core/Requests/Calendar/TentativeEventRequest.cs

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+using CommunityToolkit.Mvvm.Messaging;
+using Wino.Core.Domain.Entities.Calendar;
+using Wino.Core.Domain.Enums;
+using Wino.Core.Domain.Models.Requests;
+using Wino.Messaging.Client.Calendar;
+
+namespace Wino.Core.Requests.Calendar;
+
+/// <summary>
+/// Request to tentatively accept a calendar event invitation on the server.
+/// The calendar item status should be updated locally before queuing this request.
+/// </summary>
+public record TentativeEventRequest(CalendarItem Item, string ResponseMessage = null) : CalendarRequestBase(Item)
+{
+    private readonly CalendarItemStatus _previousStatus = Item.Status;
+
+    public override CalendarSynchronizerOperation Operation => CalendarSynchronizerOperation.TentativeEvent;
+
+    /// <summary>
+    /// After successful tentative acceptance, we need to resync to get updated status.
+    /// </summary>
+    public override int ResynchronizationDelay => 2000;
+
+    public override void ApplyUIChanges()
+    {
+        // Update the item status locally
+        Item.Status = CalendarItemStatus.Tentative;
+        
+        // Notify UI that the event status was updated
+        WeakReferenceMessenger.Default.Send(new CalendarItemUpdated(Item));
+    }
+
+    public override void RevertUIChanges()
+    {
+        // If tentative acceptance fails, revert to the previous status
+        Item.Status = _previousStatus;
+        WeakReferenceMessenger.Default.Send(new CalendarItemUpdated(Item));
+    }
+}