Add OnlyOffice integration for Seafile

- seafile/onlyoffice.yml: OnlyOffice Document Server 8.1 with JWT auth
- Expose on 127.0.0.1:6233, proxied via Caddy at office.alogins.net
- Caddyfile: add office.alogins.net → localhost:6233
- JWT secret stored in Vaultwarden (ONLYOFFICE_JWT_SECRET)
- seahub_settings.py configured inside container with ENABLE_ONLYOFFICE=True

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

seafile/onlyoffice.yml

@@ -0,0 +1,18 @@
+services:
+  onlyoffice:
+    image: ${ONLYOFFICE_IMAGE:-onlyoffice/documentserver:8.1.0.1}
+    container_name: seafile-onlyoffice
+    restart: unless-stopped
+    environment:
+      - JWT_ENABLED=true
+      - JWT_SECRET=${ONLYOFFICE_JWT_SECRET:?Variable is not set or empty}
+    volumes:
+      - "${ONLYOFFICE_VOLUME:-/opt/onlyoffice}:/var/lib/onlyoffice"
+    ports:
+      - "127.0.0.1:6233:80"
+    networks:
+      - seafile-net
+
+networks:
+  seafile-net:
+    name: seafile-net