test(e2e): stand up Playwright — fresh-DB server harness + sign-up helper

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

scripts/e2e.sh

@@ -0,0 +1,11 @@
+#!/usr/bin/env bash
+# E2E browser gate (SD-0002 §6.8) — Playwright against a fresh local stack.
+# Not yet part of check.sh/CI: the CI runner has no browsers (§10.6 gap).
+set -euo pipefail
+repo_root="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+cd "$repo_root/e2e"
+if [ ! -d node_modules ]; then
+  npm install
+  npx playwright install chromium
+fi
+npx playwright test "$@"