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

docs/internal/index.md

@@ -0,0 +1,25 @@
+# Infrastructure Documentation
+
+Internal documentation for the `sweet.home` homelab. Contains full topology, network
+details, credentials catalog (names only), and operational runbooks.
+
+## Quick links
+
+- [Architecture](architecture.md) — host map and service relationships
+- [Network Topology](network-topology.md) — VLANs, IPs, firewall rules
+- [Implementation Plan](implementation-plan.md) — phased rollout roadmap
+- [Host Inventory](generated/host-inventory.md) — auto-generated from Ansible inventory
+- [Service Catalog](generated/service-catalog.md) — auto-generated from compose files
+
+## Repo structure
+
+```
+infrastructure/
+├── terraform/     Infrastructure state (Proxmox VMs, DNS, Pi-hole)
+├── ansible/       Configuration management (non-NixOS hosts)
+├── nixos/         NixOS flake (all NixOS hosts)
+├── stacks/
+│   ├── docker/    Main app stack (Traefik, Nextcloud, Passbolt, Gitea…)
+│   └── raspi/     Raspberry Pi edge monitoring stack
+└── docs/          This documentation
+```