test(e2e): walking-skeleton Playwright happy path + verify-e2e lane (refs #68)

tests/e2e Playwright spec drives DigiD login (jan-burger/test123) → submit →
confirmation against the compose-served portal. run-e2e-check.sh runs it inside the
compose network (node container, browser installed at runtime) so the token issuer
(keycloak:8080) matches the BFF authority (ADR-0010). Wired as verify-e2e (Makefile +
verify chain + a verify-stack CI step).

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

infra/run-e2e-check.sh

@@ -0,0 +1,25 @@
+#!/usr/bin/env bash
+#
+# Walking-skeleton e2e (S-08d) against an ALREADY-RUNNING full stack: drive the self-service portal
+# in a real browser through mock-DigiD login → submit → confirmation (login → BFF → domain).
+#
+# Runs Playwright INSIDE the compose network (a node container on `cg`), so the browser reaches
+# Keycloak by service name (keycloak:8080) — the same authority the BFF validates against, so the
+# token issuer matches (ADR-0010). The spec is copied into the container (docker cp), not mounted,
+# so it leaves no root-owned files on the host. The caller owns stack bring-up + teardown.
+set -euo pipefail
+
+here="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+root="$(cd "$here/.." && pwd)"
+
+ss="$(docker ps -q --filter 'name=self-service' | head -1)"
+[ -n "$ss" ] || { echo "ERROR: no running self-service container — bring the stack up first" >&2; exit 1; }
+net="$(docker inspect -f '{{range $k,$_ := .NetworkSettings.Networks}}{{$k}}{{"\n"}}{{end}}' "$ss" | head -1)"
+echo ">> running Playwright e2e on network $net against http://self-service"
+
+cid="$(docker create --network "$net" -w /e2e --ipc=host \
+  -e SELF_SERVICE_URL=http://self-service \
+  node:24 sh -c 'npm install --no-audit --no-fund && npx playwright install --with-deps chromium && npx playwright test')"
+trap 'docker rm -f "$cid" >/dev/null 2>&1 || true' EXIT
+docker cp "$root/tests/e2e/." "$cid:/e2e" >/dev/null
+docker start -a "$cid"