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/modules/docker_container_placeholder/README.md

@@ -0,0 +1,6 @@
+# docker_container_placeholder module
+
+Placeholder module directory for future shared Docker container patterns.
+
+This is intentionally empty during initial import-first adoption.
+Keep per-container resources explicit in `../../docker/main.tf` until stable patterns emerge.

terraform/modules/proxmox_vm_placeholder/README.md

@@ -0,0 +1,6 @@
+# proxmox_vm_placeholder module
+
+Placeholder module directory for future shared Proxmox VM patterns.
+
+This is intentionally empty until provider schemas, import ID formats,
+and non-destructive reconciliation strategy are validated.