Polish answer notifications and editing controls.

Brand notification emails, log accepted sends, and keep answer editing collapsed until explicitly opened.

internal/web/server.go

@@ -543,7 +543,9 @@ func (s *Server) notifyQuestionAnswered(q *store.RankedQuestion, answerBody, adm
 		defer cancel()
 		if err := s.cfg.Mail.NotifyQuestionAnswered(ctx, msg); err != nil {
 			log.Printf("notify answer %s: %v", q.ID, err)
+			return
 		}
+		log.Printf("notify answer %s: accepted", q.ID)
 	}()
 }