fix(delete): run delete hooks and queries in one transaction

- resolvespec/restheadspec: single and batch delete use one transaction
- add sqlmock tests for delete transaction behaviour
- testmodels: serial integer ids; update tests accordingly
- add compose testserver, smoke script, podman-first Makefile targets

scripts/testserver-smoke.sh

@@ -0,0 +1,35 @@
+#!/usr/bin/env bash
+# Delete-path smoke test against the compose test server.
+# Usage: scripts/testserver-smoke.sh [base_url]   (COMPOSE overrides the compose command)
+set -euo pipefail
+
+BASE="${1:-http://localhost:8080}"
+if [ -z "${COMPOSE:-}" ]; then
+  if command -v podman >/dev/null 2>&1; then COMPOSE="podman compose"; else COMPOSE="docker compose"; fi
+fi
+TS="$(date +%s)"
+BODY="$(mktemp)"
+trap 'rm -f "$BODY"' EXIT
+
+# call <json> [path-suffix] -> prints HTTP status, body in $BODY
+call() {
+  curl -s -o "$BODY" -w '%{http_code}' -X POST "$BASE/public/departments${2:-}" \
+    -H 'Content-Type: application/json' -d "$1"
+}
+expect() { # name want got
+  if [ "$2" != "$3" ]; then echo "FAIL $1: want $2 got $3: $(cat "$BODY")"; exit 1; fi
+  echo "ok   $1 ($3)"
+}
+ids() { grep -o '"id":[0-9]*' "$BODY" | cut -d: -f2; }
+
+expect create 200 "$(call "{\"operation\":\"create\",\"data\":{\"name\":\"Smoke\",\"code\":\"S$TS\"}}")"
+ID="$(ids | head -1)"
+expect delete 200 "$(call '{"operation":"delete"}' "/$ID")"
+expect delete-again 404 "$(call '{"operation":"delete"}' "/$ID")"
+
+expect batch-create 200 "$(call "{\"operation\":\"create\",\"data\":[{\"name\":\"B\",\"code\":\"B1$TS\"},{\"name\":\"B\",\"code\":\"B2$TS\"}]}")"
+B1="$(ids | sed -n 1p)"; B2="$(ids | sed -n 2p)"
+expect batch-delete 200 "$(call "{\"operation\":\"delete\",\"data\":[\"$B1\",\"$B2\"]}")"
+
+echo "--- dbtrace"
+$COMPOSE logs testserver 2>&1 | grep 'dbtrace' | tail -20 || true