docs: rewrite README with structured overview and quick start guide

Replaces the minimal project description with a comprehensive README
including a component overview table, quick start instructions, common
Ansible operations, and links to detailed documentation. Aligns with
Red Panda Approval™ standards.

ansible/roles/incus_storage_bucket/meta/main.yml

@@ -0,0 +1,22 @@
+---
+# Role metadata and dependencies
+
+galaxy_info:
+  author: Agathos Project
+  description: Manages Incus S3-compatible storage buckets with Ansible Vault credential storage
+  license: MIT
+  min_ansible_version: "2.9"
+  platforms:
+    - name: Ubuntu
+      versions:
+        - noble
+        - plucky
+        - questing
+
+dependencies: []
+
+# Requirements:
+# - User running the playbook must be a member of the 'incus' group
+# - Incus CLI must be configured and accessible
+# - ANSIBLE_VAULT_PASSWORD_FILE environment variable must be set
+# - ansible-vault command must be available in PATH