Add the compose_stack role, inventory and playbooks

One role that syncs a payload and brings the stack up, configured entirely
through stack_* variables, plus six playbooks that each demonstrate one part
of that contract. Every playbook runs standalone and is tagged with its
stack name, so site.yml --tags <stack> works.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>

ansible/playbooks/static-site.yml

@@ -0,0 +1,16 @@
+---
+# The reference playbook. Most stacks look exactly like this: a name, the
+# networks the compose file declares external, and nothing else. Copy this file
+# when you add a service, and only reach for the rest of the contract when the
+# stack genuinely needs it.
+- name: Deploy the static site
+  hosts: app
+  gather_facts: false
+  tags: [static-site]
+
+  roles:
+    - role: compose_stack
+      vars:
+        stack_name: static-site
+        stack_networks:
+          - proxy-net