Add dockerized Playwright E2E (todo §1); screenshot live pages + foundation mockups, assert shared design-system styles match

Dockerfile.e2e

@@ -0,0 +1,12 @@
+# Playwright runner — browsers preinstalled, pinned to match @playwright/test in e2e/.
+# Built/run via compose.e2e.yml; targets the `web` service over the network.
+FROM mcr.microsoft.com/playwright:v1.49.1-noble
+
+WORKDIR /e2e
+
+COPY e2e/package.json e2e/package-lock.json ./
+RUN npm ci
+
+COPY e2e/ ./
+
+CMD ["npx", "playwright", "test"]