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/markov.go

@@ -100,8 +100,9 @@ func (p *MarkovPlugin) handleMarkov(ctx MessageContext) error {
 		targetUser = ctx.Sender
 	default:
 		// Treat as user ID
-		cleaned := strings.TrimSpace(strings.TrimPrefix(args, "@"))
-		targetUser = id.UserID(cleaned)
+		if resolved, ok := p.ResolveUser(args); ok {
+			targetUser = resolved
+		}
 	}
 
 	// Fetch corpus for the user