fix(ci): unbreak backend format, storybook-a11y, and e2e jobs

- backend: dotnet format the WP-51 migration (2-space indent, no BOM)
  to match .editorconfig — dotnet format --verify-no-changes was failing.
- storybook: stub FeatureFlagStore (WP-47) in shell/site-header stories
  alongside AccessStore, fixing NG0201 no-provider errors; bump the
  storybook-a11y container's memory cap 4g→6g (build-storybook +
  compodoc measured ~5.8GB peak RSS, leaving too little headroom).
- backend: fix a startup-breaking bug in the new (WP-52) POST
  /zgw/notificaties handler — it took ZgwOptions as a minimal-API
  parameter, which isn't registered in DI, so ASP.NET's endpoint-table
  build threw on every request once the route was registered (incl.
  /swagger, which is why Playwright's webServer health check timed
  out). Close over the existing `zgw` local instead.
- e2e: brief-v2.spec.ts's "Voorbeeld" button locator was ambiguous
  once a second "Voorbeeld met testwaarden" button existed (Playwright
  name matching is substring-based) — added `exact: true`. Also fixed
  the sent-letter preview flow to match app-letter-composer's actual
  behavior (single click → fetch, no in-page dialog, unlike
  app-behandel-scherm's), and fixed a watermark assertion that checked
  for the always-present `.preview-watermark` CSS class name instead
  of the conditionally-rendered "VOORBEELD" marker text.

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

.github/workflows/ci.yml

@@ -49,11 +49,13 @@ jobs:
     # Hard resource ceiling so a runaway test-storybook (one headless Chromium per Jest
     # worker) can't OOM the runner host — it fails its own container instead. The real cap
     # is `--maxWorkers=2` in test-storybook:ci; this is the belt-and-suspenders guardrail.
+    # 6g (was 4g): build-storybook alone (compodoc + full Angular AOT build) measured ~5.8GB
+    # peak RSS locally, leaving too little headroom at 4g.
     # NB: requires the Gitea act_runner to allow container jobs (docker mode). If the runner
     # is host-only, drop this `container:` block and rely on the worker cap alone.
     container:
       image: node:24-bookworm
-      options: --cpus=2 --memory=4g --memory-swap=4g
+      options: --cpus=2 --memory=6g --memory-swap=6g
     timeout-minutes: 15
     steps:
       - uses: actions/checkout@v4