Add horoscope, !time @user, profile achievements; fix mention detection and multiple bugs

- Add !horoscope command and daily horoscope digest using Free Horoscope API
- Enhance !time to support @user timezone lookups
- Add profile completeness achievements (birthday, timezone, both set)
- Fix Matrix mention detection in reputation and LLM passive plugins
- Fix !whois reputation query (reason string mismatch and calculation)
- Fix !time IANA case-sensitivity and username/city collision
- Fix timezone default to empty string for achievement detection
- Scope all leaderboards to room members (XP, rep, potty, insult, first, rankings, emoji)
- Fix XP rank calculation to handle tied scores correctly
- Replace skull emoji with bomb for bot insult reactions

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/plugin/urls.go

@@ -62,6 +62,11 @@ func (p *URLsPlugin) OnMessage(ctx MessageContext) error {
 	}
 
 	for _, u := range urls {
+		// Skip Matrix internal links (user mentions, room links, etc.)
+		if strings.Contains(u, "matrix.to/") {
+			continue
+		}
+
 		title, desc, err := p.fetchPreview(u)
 		if err != nil {
 			slog.Debug("urls: fetch preview failed", "url", u, "err", err)