[infra] Unify self-hosted deployment paths in getting-started.sh

Make getting-started.sh the single entry point for all self-hosted
deployments. The wizard now asks two independent questions - identity
provider (built-in vs standalone OIDC) and architecture (combined
netbird-server vs separate management/signal/relay containers) - and
renders the matching Docker Compose deployment with full reverse-proxy
parity (built-in Traefik, external Traefik, Nginx, NPM, Caddy, manual).

Highlights:
- setup.env contract: every wizard answer is persisted; --non-interactive
  re-renders idempotently from the file (IaC), --render-only generates
  without starting services. Secrets are generated once and appended so
  re-renders never rotate them.
- Split architecture renders a modern management.json (embedded Dex or
  external OIDC via PKCE), drops coturn entirely (the relay container
  serves STUN via NB_ENABLE_STUN), and optionally adds a PostgreSQL
  container when the postgres engine is selected without a DSN.
- The standalone-IdP path is framed around its real differentiator:
  multi-account support. The built-in IdP supports external SSO
  connectors but enforces single account mode.
- configure.sh, getting-started-with-dex.sh and
  getting-started-with-zitadel.sh print deprecation banners; their
  templates are frozen pending removal.
- New tests/test-render.sh validates all 8 combos (JSON validity,
  compose config, idempotent re-render, combined+external rejection)
  and runs in CI as the test-render-matrix job.

.github/workflows/test-infrastructure-files.yml

@@ -16,6 +16,20 @@ concurrency:
   cancel-in-progress: true
 
 jobs:
+  test-render-matrix:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Install jq
+        run: sudo apt-get install -y jq
+
+      - name: Checkout code
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          persist-credentials: false
+
+      - name: Run getting-started.sh render tests
+        run: bash infrastructure_files/tests/test-render.sh
+
   test-docker-compose:
     runs-on: ubuntu-latest
     strategy: