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>

.gitignore

@@ -1,15 +1,15 @@
+# Binary archives — no diff value in git
+*.zip
+*.tar.gz
+*.tar.zst
+
+# Editor temp files
+*.swp
+*.bak
+*~
+.DS_Store
+
 # Credentials - NEVER commit
 credentials
 credentials.bak
 *.credentials
-
-# Backup files
-*.bak
-*.backup
-*~
-
-# Editor files
-.vscode/
-.idea/
-*.swp
-*.swo