Add sx documentation app (sx.rose-ash.com)

New public-facing service documenting the s-expression rendering engine.
Modelled on four.htmx.org with violet theme, all content rendered via sx.

Sections: docs, reference, protocols, examples (live demos), essays
(including "sx sucks"). No database — purely static documentation.

Port 8012, Redis DB 10. CI and deploy.sh updated with app_dir() mapping
for sx_docs -> sx/ directory. Caddy reverse proxy entry added separately.

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

docker-compose.yml

@@ -35,6 +35,7 @@ x-app-env: &app-env
   APP_URL_ORDERS: https://orders.rose-ash.com
   APP_URL_RELATIONS: http://relations:8000
   APP_URL_LIKES: http://likes:8000
+  APP_URL_SX: https://sx.rose-ash.com
   APP_URL_TEST: https://test.rose-ash.com
   APP_URL_ARTDAG: https://celery-artdag.rose-ash.com
   APP_URL_ARTDAG_L2: https://artdag.rose-ash.com
@@ -47,6 +48,7 @@ x-app-env: &app-env
   INTERNAL_URL_ORDERS: http://orders:8000
   INTERNAL_URL_RELATIONS: http://relations:8000
   INTERNAL_URL_LIKES: http://likes:8000
+  INTERNAL_URL_SX: http://sx_docs:8000
   INTERNAL_URL_TEST: http://test:8000
   INTERNAL_URL_ARTDAG: http://l1-server:8100
   AP_DOMAIN: federation.rose-ash.com
@@ -214,6 +216,17 @@ services:
       REDIS_URL: redis://redis:6379/9
       WORKERS: "1"
 
+  sx_docs:
+    <<: *app-common
+    image: registry.rose-ash.com:5000/sx_docs:latest
+    build:
+      context: .
+      dockerfile: sx/Dockerfile
+    environment:
+      <<: *app-env
+      REDIS_URL: redis://redis:6379/10
+      WORKERS: "1"
+
   db:
     image: postgres:16
     environment: