feat(dubai-time): add checkTime formatter for HH:MM Dubai timestamps

Manual update checks now display the time checked in Dubai timezone.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012ZiTXPbPCSjzPVsfoweAbp

Sources/ShotdeckCore/Support/DubaiTime.swift

@@ -3,6 +3,7 @@ import Foundation
 public enum DubaiTime {
     private static let stampFormatter = LockedDateFormatter(dateFormat: "d MMM yyyy, HH:mm 'Dubai'")
     private static let fileStampFormatter = LockedDateFormatter(dateFormat: "yyyyMMdd-HHmmss")
+    private static let checkTimeFormatter = LockedDateFormatter(dateFormat: "HH:mm 'Dubai'")
 
     public static func stamp(_ date: Date) -> String {
         stampFormatter.string(from: date)
@@ -11,6 +12,10 @@ public enum DubaiTime {
     public static func fileStamp(_ date: Date) -> String {
         fileStampFormatter.string(from: date)
     }
+
+    public static func checkTime(_ date: Date) -> String {
+        checkTimeFormatter.string(from: date)
+    }
 }
 
 /// DateFormatter is not Sendable. This holder is the only shared mutable state