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/howami.go

@@ -56,9 +56,8 @@ func (p *HowAmIPlugin) OnMessage(ctx MessageContext) error {
 	target := ctx.Sender
 	args := strings.TrimSpace(p.GetArgs(ctx.Body, "howami"))
 	if args != "" {
-		cleaned := strings.TrimSpace(strings.TrimPrefix(args, "@"))
-		if cleaned != "" {
-			target = id.UserID(cleaned)
+		if resolved, ok := p.ResolveUser(args); ok {
+			target = resolved
 		}
 	}