refactor: improve project structure, idempotency, and security

- Replace interactive python setup script with native Ansible vars_prompt.

- Add missing Prometheus helm values template for resource management on Raspberry Pi.

- Replace deprecated apt_key module usage with modern keyring file download.

- Add project files: requirements.txt, requirements.yml, and .gitignore.

inventory.ini

@@ -1,2 +1,2 @@
 [pis]
-pi_node1 ansible_host={{IP}} ansible_user={{USER}} ansible_ssh_private_key_file=~/.ssh/id_rsa
+pi_node1 ansible_host="{{ target_ip }}" ansible_user="{{ target_user }}" ansible_ssh_private_key_file=~/.ssh/id_rsa