fix: move extra_hosts to outline-sync-ts container

extra_hosts is incompatible with network_mode: service:... — move it to the
Tailscale sidecar container whose network namespace is shared with outline-sync-ui.

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

docker-compose.yml

@@ -17,6 +17,8 @@ services:
     cap_add:
       - NET_ADMIN
       - NET_RAW
+    extra_hosts:
+      - "outline:100.104.53.109"
     restart: unless-stopped
     networks:
       - default
@@ -43,8 +45,6 @@ services:
     environment:
       - OUTLINE_URL=${OUTLINE_URL:-http://outline:3000}
       - OUTLINE_TOKEN=${OUTLINE_TOKEN}
-    extra_hosts:
-      - "outline:100.104.53.109"
 
 volumes:
   tailscale-state: