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>

synapse_homeserver.yaml.sanitized

@@ -0,0 +1,54 @@
+server_name: "echo6.co"
+public_baseurl: "https://matrix.echo6.co/"
+pid_file: /data/homeserver.pid
+
+listeners:
+  - port: 8008
+    type: http
+    tls: false
+    x_forwarded: true
+    bind_addresses: ["0.0.0.0"]
+    resources:
+      - names: [client, federation]
+        compress: false
+
+database:
+  name: psycopg2
+  args:
+    user: synapse
+    password: <REDACTED>
+    database: synapse
+    host: matrix-postgres
+    port: 5432
+    cp_min: 5
+    cp_max: 10
+
+log_config: "/data/echo6.co.log.config"
+media_store_path: /data/media_store
+enable_registration: false
+url_preview_enabled: true
+url_preview_ip_range_blacklist:
+  - "127.0.0.0/8"
+  - "10.0.0.0/8"
+  - "172.16.0.0/12"
+  - "192.168.0.0/16"
+  - "100.64.0.0/10"
+  - "169.254.0.0/16"
+  - "::1/128"
+  - "fe80::/10"
+  - "fc00::/7"
+
+registration_shared_secret: <REDACTED>
+macaroon_secret_key: <REDACTED>
+form_secret: <REDACTED>
+signing_key_path: "/data/echo6.co.signing.key"
+report_stats: false
+
+trusted_key_servers:
+  - server_name: "matrix.org"
+
+# MAS delegation - replaces oidc_providers
+matrix_authentication_service:
+  enabled: true
+  endpoint: http://matrix-mas:8080/
+  secret: <REDACTED>