docs: Phase 11 follow-on — fix inter-doc cross-references in deeper subdirs

Per Phase 1 audit at cowork/docs-overhaul-phase-1-audit-2026-05-04/.
Continuation of Phase 11 (commit a7b36c4 handled README + first round
of docs/ links). This commit fixes the remaining inter-doc broken
links in the deeper subdirectories.

Per source directory:

  docs/getting-started/quickstart.md (1 fix):
    (connectors.md) → (../reference/connectors/index.md)

  docs/contributor/test-environment.md (2 fixes):
    (tls.md) → (../operator/tls.md)
    (upgrade-to-tls.md) → (../archive/upgrades/to-tls-v2.2.md)

  docs/contributor/testing-strategy.md (4 fixes):
    `docs/security.md` → `docs/operator/security.md`
    (security.md) → (../operator/security.md)
    `docs/testing-guide.md` (kept; testing-guide.md still at top level
      pending Phase 5 prune)
    (testing-guide.md) → (../testing-guide.md)

  docs/migration/acme-from-traefik.md (2 sites, multi-link):
    (./acme-cert-manager-walkthrough.md) → (./acme-from-cert-manager.md)
    (./acme-server.md) → (../reference/protocols/acme-server.md)

  docs/migration/cert-manager-coexistence.md (1 fix):
    (./quickstart.md) → (../getting-started/quickstart.md)

  docs/migration/from-acmesh.md (2 fixes):
    (connectors.md) → (../reference/connectors/index.md)
    (./examples.md) → (../getting-started/examples.md)

  docs/migration/acme-from-caddy.md (multi-link):
    (./acme-cert-manager-walkthrough.md) → (./acme-from-cert-manager.md)
    (./acme-server.md) → (../reference/protocols/acme-server.md)

  docs/migration/acme-from-cert-manager.md (multi-link):
    (./acme-server.md) → (../reference/protocols/acme-server.md)
    (./acme-server-threat-model.md) → (../reference/protocols/acme-server-threat-model.md)
    (./acme-caddy-walkthrough.md) → (./acme-from-caddy.md)
    (./acme-traefik-walkthrough.md) → (./acme-from-traefik.md)

  docs/migration/from-certbot.md (2 fixes):
    (./concepts.md) → (../getting-started/concepts.md)
    (./examples.md) → (../getting-started/examples.md)

  docs/operator/tls.md (3 sites):
    (upgrade-to-tls.md) → (../archive/upgrades/to-tls-v2.2.md)
    (quickstart.md) → (../getting-started/quickstart.md)
    (test-env.md) → (../contributor/test-environment.md)

  docs/operator/runbooks/disaster-recovery.md (5 fixes):
    (crl-ocsp.md) → (../../reference/protocols/crl-ocsp.md)
    (tls.md) → (../../operator/tls.md)
    (security.md) → (../../operator/security.md)
    (scep-intune.md) → (../../reference/protocols/scep-intune.md)
    (est.md) → (../../reference/protocols/est.md)

After this commit, the major operator-facing surfaces have valid
cross-refs. Some lower-traffic docs (compliance/soc2.md, compliance/
nist-sp-800-57.md, deeper reference/* docs) may still have broken
inter-doc links; those will surface during the Phase 4 follow-on
(per-connector page extraction) and Phase 5 (testing-guide prune)
work and can be fixed there incrementally.

docs/migration/acme-from-cert-manager.md

@@ -254,12 +254,12 @@ helm uninstall certctl-test
 
 ## See also
 
-- [`docs/acme-server.md`](./acme-server.md) — canonical reference.
-- [`docs/acme-server-threat-model.md`](./acme-server-threat-model.md) —
+- [`docs/acme-server.md`](../reference/protocols/acme-server.md) — canonical reference.
+- [`docs/acme-server-threat-model.md`](../reference/protocols/acme-server-threat-model.md) —
   security posture.
-- [`docs/acme-caddy-walkthrough.md`](./acme-caddy-walkthrough.md) —
+- [`docs/acme-caddy-walkthrough.md`](./acme-from-caddy.md) —
   Caddy-side recipe.
-- [`docs/acme-traefik-walkthrough.md`](./acme-traefik-walkthrough.md) —
+- [`docs/acme-traefik-walkthrough.md`](./acme-from-traefik.md) —
   Traefik-side recipe.
 - [`deploy/test/acme-integration/`](../deploy/test/acme-integration/) —
   Phase 5 integration test (the same recipe, automated).