Fix !post in round-robin mode, ❓ reaction VS16, image label

- !post falls back to newest unposted story for the channel when the
  in-memory queue is empty (the steady state under round-robin).
- Accept ❓️/❔️ (U+FE0F variation selector) as question reactions —
  the bare codepoints alone missed clients that render the colored emoji.
- Rewrite Guardian i.guim.co.uk thumbnails to width=1200 so we stop
  rejecting real images as "tracking pixels"; relabel the size warning.
- Log decrypt failures and reactions on events not in post_log so future
  silent drops surface instead of vanishing.

internal/ingestion/parser.go

@@ -55,7 +55,7 @@ func FetchFeed(feedURL string) ([]FeedItem, error) {
 			GUID:       itemGUID(item),
 			Headline:   strings.TrimSpace(item.Title),
 			Lede:       extractLede(item.Description),
-			ImageURL:   extractImageURL(item),
+			ImageURL:   NormalizeImageURL(extractImageURL(item)),
 			ArticleURL: strings.TrimSpace(item.Link),
 		}
 		if fi.GUID == "" || fi.ArticleURL == "" {