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/proxmox/pihole.tf

@@ -0,0 +1,14 @@
+# Pi-hole VM — DECOMMISSIONED
+# Pi-hole was decommissioned. DNS is now handled by FreeIPA (domain-controller.sweet.home).
+# DHCP is on the router. PXE DHCP is handled by the pxe-boot LXC.
+#
+# This resource block is kept as historical documentation of VMID 108.
+# If the VM has been destroyed on Proxmox, remove this file entirely.
+# If it still exists and needs to be removed via Terraform:
+#   terraform destroy -target=proxmox_virtual_environment_vm.pihole
+
+# resource "proxmox_virtual_environment_vm" "pihole" {
+#   name      = "pihole"
+#   node_name = "pve"
+#   vm_id     = 108
+# }