feat(ci): add automated post-deploy production rollout verification (#39)

### Summary of Changes

- **Version Metadata Generation**:
- `ci/docker/www/Dockerfile` & `ci/docker/docs/Dockerfile` accept
`COMMIT_SHA` and `VERSION` build args and write
`/usr/share/nginx/html/version.json`.
- `ci/config/nginx/default.conf` configures `location = /version.json`
with `Cache-Control: no-store, no-cache, must-revalidate` so
verification is never stale.
- **Automated Rollout Verification**:
  - `.github/workflows/services-www-releases-dispatch-release.yml`
  - `.github/workflows/services-docs-next-required.yml`
  - `.github/workflows/services-www-next-required.yml`
- Added `verify-rollout` job that polls
`https://www.ermnvldmr.com/version.json` and
`https://docs.ermnvldmr.com/version.json` with 10s intervals (up to 5
minutes) to ensure the commit actively rolls out to users.

ci/docker/www/Dockerfile

@@ -37,8 +37,15 @@ RUN pnpm --filter @ermnvldmr/www build:all
 # Stage 2: Runtime
 FROM nginx:alpine
 
+ARG COMMIT_SHA="unknown"
+ARG VERSION="latest"
+
 COPY --from=builder /app/services/www/dist /usr/share/nginx/html
 COPY ci/config/nginx/default.conf /etc/nginx/conf.d/default.conf
 
+# Generate version metadata for automated rollout verification
+RUN printf '{\n  "service": "www",\n  "version": "%s",\n  "commit": "%s",\n  "builtAt": "%s"\n}\n' \
+    "${VERSION}" "${COMMIT_SHA}" "$(date -u +'%Y-%m-%dT%H:%M:%SZ')" > /usr/share/nginx/html/version.json
+
 EXPOSE 80
 CMD ["nginx", "-g", "daemon off;"]