docs: re-verify netbird-zero-trust.md, no content drift found

Live-checked the container roster (exact version match), the Caddyfile
splitter config (byte-for-byte match), and mesh connectivity
(Management/Signal both confirmed connected). Peer-roster/policy-list
screenshots not independently re-verified (no accessible NetBird API
token - it's a manual dashboard PAT, not Vault/ansible-managed), but
nothing else indicates drift. Both diagrams still accurate. Bumping
verified date/SHAs only.

docs/netbird-zero-trust.md

@@ -1,6 +1,6 @@
-<!-- verified: 2026-09-06
+<!-- verified: 2026-09-19
      netbird-lxc@13b5d80 : netbird/Caddyfile, netbird/docker-compose.yaml, netbird/config.yaml.ctmpl
-     iac@49ff427 : ansible/roles/secure_vault/netbird_agent, terraform/containers.tf
+     iac@f770e1c : ansible/roles/secure_vault/netbird_agent, terraform/containers.tf
      trilium : qWLU4xqYLdJ3, oYuIjaczDrZA, nAPJq9A1iuX8, Cl4TWBZ7ytYr
 -->