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

ansible/roles/proxmox-hardening/templates/cluster-fw.j2

@@ -0,0 +1,27 @@
+# Managed by ansible proxmox-hardening role — do not edit by hand
+# Proxmox datacenter-level firewall (Stage 1: single-node management access only)
+# Stage 2 (Corosync/Ceph cluster) rules remain commented until needed.
+
+[OPTIONS]
+enable: 1
+policy_in: DROP
+policy_out: ACCEPT
+
+[IPSET mgmt]
+# Management subnet — SSH and web UI access only from here
+{{ proxmox_mgmt_cidr }}
+
+[RULES]
+# Allow SSH from management network
+IN ACCEPT -source +mgmt -p tcp --dport 22 -log nolog
+# Allow PVE web UI from management network
+IN ACCEPT -source +mgmt -p tcp --dport 8006 -log nolog
+# Allow SPICE console from management network
+IN ACCEPT -source +mgmt -p tcp --dport 3128 -log nolog
+
+# Stage 2 — Corosync (uncomment when clustering pve1 with additional nodes)
+# IN ACCEPT -source +mgmt -p udp --dport 5404:5405 -log nolog
+
+# Stage 2 — Ceph (uncomment when Ceph OSD replication is active)
+# IN ACCEPT -source +mgmt -p tcp --dport 6800:7568 -log nolog
+