fix(httpapi): stable problem details for client errors

Стабильные detail для 4xx (store, CDN preview, CSV); логирование на сервере. Расширен lint-httpapi для ERR-01 в 4xx.

Co-authored-by: Cursor <[email protected]>

scripts/lint-httpapi.sh

@@ -16,6 +16,14 @@ if grep -rE 'writeProblem\(w, http\.StatusBadGateway.*err\.Error\(\)' "$HTTPAPI"
   FAIL=1
 fi
 
+echo "==> ERR-01: no err.Error() in 4xx writeProblem (store/cdn/csv)"
+if grep -rE 'writeProblem\(w, http\.Status(NotFound|UnprocessableEntity|BadRequest).*, err\.Error\(\)' "$HTTPAPI" 2>/dev/null; then
+  FAIL=1
+fi
+if grep -rE 'writeStoreErr.*err\.Error|writeProblem.*Unprocessable.*err\.Error' "$HTTPAPI" 2>/dev/null; then
+  FAIL=1
+fi
+
 echo "==> ARCH-01: no SQL/pgx queries in httpapi"
 if grep -rE 'pool\.(Query|Exec|QueryRow)|SELECT |INSERT INTO |UPDATE .* SET |DELETE FROM ' "$HTTPAPI" 2>/dev/null; then
   FAIL=1