Remove legacy question storage (#7)

Deletes obsolete question/answer/vote persistence and the compatibility answer endpoint. Existing databases drop the legacy tables through migration 009. Plumber replies now notify the root homeowner even when nested beneath another plumber reply. Post and reply forms prevent duplicate submissions and show progress while posting.

Reviewed-on: #7
Co-authored-by: codegirl-007 <s.raide@gmail.com>

internal/web/posts.go

@@ -93,7 +93,8 @@ func (s *Server) handleCreatePost(w http.ResponseWriter, r *http.Request) {
 	)
 }
 
-// notifyPostReply asynchronously emails the direct parent post's author.
+// notifyPostReply emails the root homeowner for admin replies and the direct
+// parent author for homeowner replies.
 func (s *Server) notifyPostReply(
 	parent *store.Post,
 	root *store.Post,
@@ -104,13 +105,19 @@ func (s *Server) notifyPostReply(
 		root == nil ||
 		reply == nil ||
 		replyAuthor == nil ||
-		s.cfg.Mail == nil ||
-		parent.AuthorID == replyAuthor.ID {
+		s.cfg.Mail == nil {
 		return
 	}
 	if _, disabled := s.cfg.Mail.(mail.Nop); disabled {
 		return
 	}
+	recipientID := parent.AuthorID
+	if replyAuthor.Admin() {
+		recipientID = root.AuthorID
+	}
+	if recipientID == replyAuthor.ID {
+		return
+	}
 	msg := mail.PostReply{
 		RootID:          root.ID,
 		RootTitle:       root.Title,
@@ -118,7 +125,6 @@ func (s *Server) notifyPostReply(
 		ReplyBody:       reply.Body,
 		ReplyAuthorName: replyAuthor.Name,
 	}
-	recipientID := parent.AuthorID
 	go func() {
 		ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
 		defer cancel()