feat: add admin apis

internal/model/social.go

@@ -245,6 +245,10 @@ type Notification struct {
 	// the client can deep-link to the post for kinds where the actor isn't
 	// the post owner (e.g. comment_reply). Nil when there's no post.
 	PostAuthorHandle *string `json:"post_author_handle,omitempty"`
+
+	// Body carries free text for the 'admin_message' kind (an admin → user
+	// direct message). Nil for every event-driven kind.
+	Body *string `json:"body,omitempty"`
 }
 
 // PushSubscription is one browser/device Web Push endpoint a user granted.