support PWA notification.

API/ROLAC.API/Services/Notifications/NotificationModels.cs

@@ -3,8 +3,9 @@ namespace ROLAC.API.Services.Notifications;
 /// <summary>Canonical channel discriminators stored in NotificationLog.Channel.</summary>
 public static class NotificationChannels
 {
-    public const string Email = "email";
-    public const string Line  = "line";
+    public const string Email   = "email";
+    public const string Line    = "line";
+    public const string WebPush = "webpush";
 }
 
 /// <summary>Canonical target-type discriminators stored in NotificationLog.TargetType.</summary>
@@ -36,6 +37,12 @@ public sealed record NotificationResult(
 /// <summary>A file attached to an outbound email.</summary>
 public sealed record EmailAttachment(string FileName, string ContentType, byte[] Content);
 
+/// <summary>
+/// The content of a single Web Push notification. <see cref="Url"/> is the in-app path to open when
+/// the notification is clicked; <see cref="Tag"/> lets a newer notification replace an older one.
+/// </summary>
+public sealed record WebPushPayload(string Title, string Body, string? Url = null, string? Tag = null);
+
 /// <summary>
 /// A request to send one email to a set of members (resolved via Member.Email) and/or raw
 /// addresses. The caller supplies the final HTML body — no templating in this phase.