feat(ops): add database readiness probe

deploy/README.md

@@ -305,9 +305,13 @@ than merely "running".
 - **Backend:** `curl -fsS http://127.0.0.1:8080/health`. Anonymous, and deliberately **does not touch
   the database** — a health check that queried MariaDB would restart a healthy backend whenever the
   database blipped. `start_period` is 90s to cover first-boot schema reconciliation.
+- **API/database readiness:** `curl -fsS https://<host>/ready`. This checks that the API can reach its
+  configured database and returns only `ready` or `unavailable`; detailed diagnostics remain admin-only.
+  Deployment validation requires this probe, while Docker restart policy continues to use liveness.
 - **Frontend:** `wget` against nginx on port 80.
 - `frontend` waits for `backend` to be *healthy*, not merely started, because nginx proxies `/api` to
   it and refuses to start if the upstream cannot be resolved.
 
-A backend that cannot reach its database exits and is reported `unhealthy`, so a broken deploy does not
-present as a running stack.
+A backend that cannot reach its database during startup exits and is reported `unhealthy`. A dependency
+failure after startup leaves the process alive but makes `/ready` return 503, so deployment validation
+cannot mistake a live-but-unready stack for a successful release.

deploy/deploy.sh

@@ -550,6 +550,16 @@ if ! curl -fsS "${public_base}/" >/dev/null; then
   exit 1
 fi
 
+if ! curl -fsS "${public_base}/health" >/dev/null; then
+  echo "Public API liveness check failed for ${public_base}/health"
+  exit 1
+fi
+
+if ! curl -fsS "${public_base}/ready" >/dev/null; then
+  echo "Public API/database readiness check failed for ${public_base}/ready"
+  exit 1
+fi
+
 if ! curl -fsS -D "$auth_config_headers_file" -o "$auth_config_body_file" "${public_base}/api/auth/config"; then
   echo "Public API smoke check failed for ${public_base}/api/auth/config"
   exit 1