Migration: consolidate Echo6 docs to cortex with full infrastructure cleanup sync

- Documents recent infrastructure cleanup (8 CTs destroyed, 35 DNS records removed, Headscale cleanup)
- Adds 24 new runbooks covering Authentik, PeerTube, Meshtastic, RECON, Proxmox, Mailcow, Internet Archive, GPU routing
- Adds project documentation for headscale, vaultwarden, peertube, matrix, mmud, advbbs, arr stack
- Updates services.md, environment.md, caddy.md, authentik.md to match live infrastructure
- Removes 4 deprecated runbook duplicates (canonical versions live in projects/)
- Adds .gitignore for binary archives and editor temp files

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

runbooks/proxmox-create-ubuntu-vm.md

@@ -101,6 +101,16 @@ ssh root@$PVE_HOST "qm set $VMID \
   --boot order=scsi0"
 ```
 
+### Alternative: Use standard Echo6 cloud-init snippet
+
+If the snippet is already on the node (deployed by `echo6-onboard-node.sh`), you can use it instead of the manual `--ciuser`/`--cipassword` config above. This pre-installs sshpass, curl, git, htop, and other standard packages via cloud-init:
+
+```bash
+ssh root@$PVE_HOST "qm set $VMID --cicustom \"user=local:snippets/echo6-base-userdata.yml\""
+```
+
+**Note:** You still need `--ipconfig0`, `--nameserver`, `--searchdomain`, `--sshkeys`, and `--boot` from the block above. The snippet only covers packages and `manage_etc_hosts`.
+
 ## Step 5 — GPU Passthrough (if enabled)
 
 Skip if `GPU_PASSTHROUGH=no`.
@@ -144,7 +154,7 @@ ssh root@$PVE_HOST "qm terminal $VMID"
 
 ```bash
 ssh zvx@$VM_IP 'sudo apt-get update && sudo apt-get install -y \
-  curl wget git htop iotop tmux vim \
+  sshpass curl wget git htop iotop tmux vim \
   rsync tree jq unzip \
   net-tools dnsutils \
   python3 python3-pip python3-venv \