force jpeg format for avatar download in NSE

CDN may serve WebP by default which INImage doesn't reliably handle.
Append @jpeg to the URL to request JPEG format instead.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

modules/BlueskyNSE/NotificationService.swift

@@ -118,11 +118,19 @@ class NotificationService: UNNotificationServiceExtension {
   }
 
   func downloadAvatarImage(from urlString: String) -> INImage? {
-    let thumbnailUrlString = urlString.replacingOccurrences(
+    var thumbnailUrlString = urlString.replacingOccurrences(
       of: "/img/avatar/",
       with: "/img/avatar_thumbnail/"
     )
 
+    // CDN URLs may end with @webp or no extension (which defaults to webp).
+    // INImage doesn't reliably handle WebP, so force JPEG.
+    if let atRange = thumbnailUrlString.range(of: "@", options: .backwards) {
+      thumbnailUrlString = String(thumbnailUrlString[..<atRange.lowerBound]) + "@jpeg"
+    } else {
+      thumbnailUrlString += "@jpeg"
+    }
+
     guard let url = URL(string: thumbnailUrlString) else { return nil }
 
     var request = URLRequest(url: url)