Reach QA's published ports from the smoke-qa job container via bridge gateway

The runner executes each job in its own container on docker's default bridge
network, so "localhost" never resolves to the docker host - smoke-qa's direct
Postgres connection and Playwright/API HTTP calls need the bridge gateway IP
instead. Bind the db port to that same gateway IP (not 0.0.0.0) so it stays
reachable only from sibling containers, not off-box.

scripts/ci/lib.sh

@@ -111,6 +111,16 @@ ensure_node() {
   export PATH="$install_dir/bin:$PATH"
 }
 
+# The IP address on which a container published on 0.0.0.0/<gateway-ip> is
+# reachable from a sibling container on docker's default bridge network (i.e.
+# the docker host's bridge-side address, not its public interface). Used to
+# bind QA's db port narrowly - reachable by the smoke-qa job container, not
+# exposed off-box the way 0.0.0.0 would be.
+docker_bridge_gateway() {
+  docker network inspect bridge -f '{{(index .IPAM.Config 0).Gateway}}' 2>/dev/null \
+    || ip route show default 2>/dev/null | awk '/default/ {print $3; exit}'
+}
+
 registry_login() {
   require_registry_vars
   [[ -n "$REGISTRY_USER" ]] || fail "REGISTRY_USER env var is required to push images"