Initial infrastructure mono-repo scaffold

Consolidates nixos, docker, raspi, and debian-configuration into a single
infrastructure-as-code repo. Includes:

- ansible/: full inventory + proxmox-hardening, freeipa, and raspberrypi
  roles (converted from debian-configuration bash scripts)
- terraform/: Proxmox VMs, Dynu DNS, Pi-hole (decommissioned stub),
  Docker container catalog — migrated from docker/infrastructure/terraform/
- stacks/docker/, stacks/raspi/, nixos/: placeholder READMEs pending
  git subtree population (see implementation plan)
- docs/: internal MkDocs site with architecture, network topology, runbooks,
  and drift-detection guide; external sanitized site
- scripts/: drift-detect.sh, docs-build.sh, install-hooks.sh, check-secrets.sh
- CI: secret-scan (push/PR), drift-detect (daily), docs-build (on change)
- Pi-hole removed throughout — DNS is FreeIPA, DHCP is router

See docs/internal/implementation-plan.md for the phased rollout after
pushing to Gitea.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UvNjoxTWEDkhXsd1Dq2ETP

terraform/dns/imports.tf.example

@@ -0,0 +1,16 @@
+# Copy this file to imports.tf and adjust IDs after confirming the
+# published provider docs for import ID formats.
+# For dynu_domain, import ID is commonly the root domain name.
+
+import {
+  to = dynu_domain.lan_ddnsgeek_com
+  id = var.dynu_root_domain
+}
+
+# DNS record imports are intentionally examples only because the provider
+# requires explicit record_type/hostname in config before import.
+#
+# import {
+#   to = dynu_dns_record.grafana_lan_ddnsgeek_com
+#   id = var.dynu_record_import_id
+# }