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/s3_regenerate_key.yml

@@ -0,0 +1,34 @@
+---
+# Regenerate S3 Bucket Access Key
+# Rotates credentials for an existing Incus S3 bucket
+#
+# WARNING: This will invalidate existing credentials immediately
+#
+# Prerequisites:
+#   - User must be member of 'incus' group
+#   - Incus must be configured and accessible
+#   - Bucket must already exist
+#
+# Usage:
+#   ansible-playbook regenerate_s3_key.yml -e bucket_name=casdoor
+
+- name: Regenerate S3 Bucket Access Key
+  hosts: localhost
+  connection: local
+  gather_facts: false
+  
+  pre_tasks:
+    - name: Validate required parameters
+      ansible.builtin.assert:
+        that:
+          - bucket_name is defined
+          - bucket_name | length > 0
+        fail_msg: |
+          Missing required parameters. Usage:
+          ansible-playbook regenerate_s3_key.yml -e bucket_name=<name>
+  
+  tasks:
+    - name: Include regenerate tasks
+      ansible.builtin.include_role:
+        name: incus_storage_bucket
+        tasks_from: regenerate