Add rich text links, language filter, and domain deny feature

- Use labeled links (Article · Audio) instead of raw URLs in posts
- Add language filter dropdown to dashboard with toggle selection
- Auto-deny feeds with no language on discovery
- Add deny/undeny buttons for domains to block crawling
- Denied domains set feeds to dead status, preventing future checks

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

crawler.go

@@ -250,7 +250,10 @@ func (c *Crawler) StartPublishLoop() {
 			itemToPublish := item
 			if item.Link != "" {
 				if shortURL, err := c.GetShortURLForPost(item.Link, &item.ID, item.FeedURL); err == nil {
+					fmt.Printf("Publish: shortened %s -> %s\n", item.Link[:min(40, len(item.Link))], shortURL)
 					itemToPublish.Link = shortURL
+				} else {
+					fmt.Printf("Publish: short URL failed for %s: %v\n", item.Link[:min(40, len(item.Link))], err)
 				}
 			}
 			if item.Enclosure != nil && item.Enclosure.URL != "" {