Deploy: smoke-check the digest masthead asset (logo-email.png)

Per Codex — guard against the static logo silently going missing (which would
break the newsletter masthead). Non-fatal curl check after Caddy reload.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

deploy/publish.sh

@@ -19,4 +19,11 @@ docker compose -f "$api_compose" up -d --build
 echo "→ reloading Caddy"
 docker exec caddy caddy reload --config /etc/caddy/Caddyfile --adapter caddyfile
 
+# Non-fatal smoke check: the digest masthead points at this static asset, so a
+# missing/unserved logo-email.png would silently break the newsletter header.
+echo "→ smoke check"
+curl -fsS -o /dev/null -w '  logo-email.png → %{http_code} %{content_type}\n' \
+  https://upbeatbytes.com/logo-email.png \
+  || echo "  ⚠ logo-email.png is not being served — the digest masthead would break!"
+
 echo "✓ Published Upbeat Bytes → https://upbeatbytes.com"