Add nginx proxy for OG meta tags and CSS injection

Traefik was routing directly to Outline, so the nginx.conf
was unused. Add nginx as an intermediary service to enable
sub_filter injection of OG tags on the homepage and custom
CSS on all pages.

docker-compose.yml

@@ -1,10 +1,21 @@
 services:
+  nginx:
+    image: nginx:alpine
+    container_name: outline-nginx
+    restart: unless-stopped
+    depends_on:
+      - outline
+    volumes:
+      - ./nginx.conf:/etc/nginx/nginx.conf:ro
+      - ./theme:/opt/ghost-guild-wiki-theme:ro
+    networks:
+      - default
+      - dokploy-network
+
   outline:
     image: docker.getoutline.com/outlinewiki/outline:latest
     container_name: outline
     restart: unless-stopped
-    ports:
-      - "127.0.0.1:3100:3000"
     env_file: ./outline.env
     depends_on:
       postgres:
@@ -56,6 +67,10 @@ services:
       timeout: 5s
       retries: 5
 
+networks:
+  dokploy-network:
+    external: true
+
 volumes:
   outline-storage:
   postgres-data: