feat(ansible): add semaphore docker splash demo with dagster config

ansible-semaphore-docker-demo/README.md

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+# SemaphoreUI Docker Splash Demo
+
+Demo Ansible molto semplice, pensata per essere eseguita da SemaphoreUI:
+- `test.yml`: verifica connettivita e prerequisiti
+- `deploy.yml`: deploy di un container Nginx Docker con pagina HTML custom
+- `undeploy.yml`: rimozione container e cleanup
+
+## Struttura
+
+```text
+ansible-semaphore-docker-demo/
+  ansible.cfg
+  inventory
+  requirements.yml
+  deploy.yml
+  test.yml
+  undeploy.yml
+  group_vars/
+    all.yml
+    secrets.yml
+  roles/
+    splash/
+      tasks/main.yml
+      templates/index.html.j2
+      templates/nginx.conf.j2
+  semaphore_dagster_config.example.yml
+```
+
+## Prerequisiti host target
+
+- Linux con accesso SSH
+- Privilegi sudo/root
+- Debian/Ubuntu (nel playbook installo `docker.io` e `python3-docker`)
+
+## Uso locale rapido
+
+```bash
+cd ansible-semaphore-docker-demo
+ansible-galaxy collection install -r requirements.yml
+ansible-playbook -i inventory test.yml
+ansible-playbook -i inventory deploy.yml
+ansible-playbook -i inventory undeploy.yml
+```
+
+## Accesso app
+
+Dopo il deploy:
+- `http://<IP_SERVER>:8090`
+- healthcheck: `http://<IP_SERVER>:8090/health`
+
+## Variabili principali
+
+In `group_vars/all.yml`:
+- `app_port`
+- `greeting_message`
+- `container_name`
+- `nginx_version`
+- `accent_color`
+- `secondary_color`
+
+In `group_vars/secrets.yml`:
+- `app_secret`
+- `release_id`
+
+Per produzione: cifra `group_vars/secrets.yml` con Ansible Vault.
+
+## SemaphoreUI
+
+Per bootstrap automatico con il tuo DAG, usa il file:
+- `semaphore_dagster_config.example.yml`
+
+Basta aggiornare URL Semaphore, token API, project ID, repo URL e inventory content.