Implemented all service roles

- docker: install Docker Engine from official apt repo, configure log rotation,
  create shared traefik_public network
- traefik: reverse proxy with automatic Let's Encrypt TLS, dashboard on
  cloud.ladkau.de behind basic auth
- gitea: self-hosted Git with PostgreSQL, Git-over-SSH on port 2222
- sso: Keycloak with PostgreSQL for OIDC/OAuth2 single sign-on
- nextcloud: file storage with PostgreSQL, Redis, cron sidecar, CalDAV/CardDAV
  well-known redirects
- mail: Roundcube webmail client with PostgreSQL
- registry: Docker Registry v2 with htpasswd auth, no upload size limit
- k8s: placeholder nginx page

All secrets documented in vault.yml; runbook updated with per-service
first-run notes.

ansible/roles/sso/templates/docker-compose.yml.j2

@@ -0,0 +1,64 @@
+# Managed by Ansible — do not edit manually
+services:
+  sso-db:
+    image: postgres:{{ keycloak_db_version }}
+    container_name: sso-db
+    restart: unless-stopped
+    environment:
+      POSTGRES_USER: keycloak
+      POSTGRES_PASSWORD: "{{ keycloak_db_password }}"
+      POSTGRES_DB: keycloak
+    volumes:
+      - {{ sso_data_dir }}/db:/var/lib/postgresql/data
+    networks:
+      - sso_internal
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U keycloak"]
+      interval: 10s
+      timeout: 5s
+      retries: 5
+
+  sso-keycloak:
+    image: quay.io/keycloak/keycloak:{{ keycloak_version }}
+    container_name: sso-keycloak
+    command: start
+    restart: unless-stopped
+    environment:
+      # Database
+      KC_DB: postgres
+      KC_DB_URL: jdbc:postgresql://sso-db:5432/keycloak
+      KC_DB_USERNAME: keycloak
+      KC_DB_PASSWORD: "{{ keycloak_db_password }}"
+      # Hostname — Traefik handles TLS, Keycloak listens plain HTTP internally
+      KC_HOSTNAME: "{{ domain_sso }}"
+      KC_HTTP_ENABLED: "true"
+      KC_PROXY_HEADERS: xforwarded
+      # Health endpoint (used by Docker healthcheck)
+      KC_HEALTH_ENABLED: "true"
+      # Bootstrap admin — only used on first start; change password via UI afterwards
+      KEYCLOAK_ADMIN: "{{ keycloak_admin_user }}"
+      KEYCLOAK_ADMIN_PASSWORD: "{{ keycloak_admin_password }}"
+    networks:
+      - traefik_public
+      - sso_internal
+    labels:
+      - "traefik.enable=true"
+      - "traefik.http.routers.sso.rule=Host(`{{ domain_sso }}`)"
+      - "traefik.http.routers.sso.entrypoints=websecure"
+      - "traefik.http.routers.sso.tls.certresolver=letsencrypt"
+      - "traefik.http.services.sso.loadbalancer.server.port=8080"
+    healthcheck:
+      test: ["CMD-SHELL", "curl -f http://localhost:8080/health/ready || exit 1"]
+      interval: 30s
+      timeout: 10s
+      retries: 5
+      start_period: 90s
+    depends_on:
+      sso-db:
+        condition: service_healthy
+
+networks:
+  traefik_public:
+    external: true
+  sso_internal:
+    internal: true