docs: restore the two backlog paths RD-19's target of 0 removed

RD-18 established that a ticket reference inside a path to a document that
still exists is a pointer, not provenance, and exempted one. RD-19 did not
re-run that check against `backend/`, and asserted a target of 0. Two such
paths existed, so the agent described the two documents in prose instead. The
path no longer resolves and the reader must search.

Restore both paths, correct the ticket's decision 1 and acceptance target to
2, and record the miss as the eighth in the README's list.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

backend/README.md

@@ -15,7 +15,7 @@ status codes and error envelope are production-shaped.
 covers it, see `docker-compose.yml`) does **not** lose data. Delete the file to
 reset demo data back to empty, the same state a fresh clone starts from. This is
 a deliberate, right-sized choice for a POC (SQLite, no external DB service) — see
-the durable-persistence design note in `docs/project/backlog/`.
+`docs/project/backlog/WP-22-durable-persistence.md`.
 
 ## Run
 

backend/src/BigRegister.Api/Domain/Letters/LetterHtml.cs

@@ -151,9 +151,8 @@ public static class LetterHtml
   private static string EncLines(string s) => Enc(s).Replace("\n", "<br>");
 
   // Walks up from the running assembly's own directory (NOT the process cwd, which
-  // varies by how `dotnet run`/docker/tests invoke it — see the letter-preview-html design
-  // note in docs/project/backlog/) until
-  // it finds `public/letter.css`. docker-compose.yml bind-mounts `./public` under the
+  // varies by how `dotnet run`/docker/tests invoke it — see
+  // docs/project/backlog/WP-25-letter-preview-html.md) until it finds `public/letter.css`. docker-compose.yml bind-mounts `./public` under the
   // api container's `/src` for exactly this walk to resolve there too.
   private static string FindLetterCss()
   {