docs: cleanup pre-existing broken links in connector pages

Phase 4 structural (commit 633e440) moved 6 connector files into the
new docs/reference/connectors/ subdirectory but didn't update all
inter-doc references for the new path layout. Phase 11 caught the
high-traffic ones; this sweep gets the rest, found by the Phase 4
follow-on verification pass.

Mappings applied (relative to docs/reference/connectors/):

  deployment-atomicity.md     → ../deployment-model.md
  deployment-vendor-matrix.md → ../vendor-matrix.md
  architecture.md             → ../architecture.md
  est.md                      → ../protocols/est.md
  scep-intune.md              → ../protocols/scep-intune.md
  async-polling.md            → ../protocols/async-ca-polling.md
  quickstart.md               → ../../getting-started/quickstart.md
  demo-advanced.md            → ../../getting-started/advanced-demo.md
  legacy-est-scep.md          → ../protocols/scep-server.md
  connectors.md               → index.md

Plus prose backtick references (`docs/architecture.md` etc.) updated
to the new subdirectory paths.

Files touched: apache, f5, iis, k8s, nginx, index. 33 line changes.
Full link-check across docs/reference/connectors/*.md is now clean
(0 broken inter-doc references).

docs/reference/connectors/k8s.md

@@ -118,5 +118,5 @@ update, then re-apply if desired.
 
 ## Related docs
 
-- [Atomic deploy + post-verify + rollback](deployment-atomicity.md)
-- [Vendor compatibility matrix](deployment-vendor-matrix.md)
+- [Atomic deploy + post-verify + rollback](../deployment-model.md)
+- [Vendor compatibility matrix](../vendor-matrix.md)