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.

roles/docker/tasks/main.yml

@@ -10,14 +10,21 @@
     state: present
     update_cache: yes
 
-- name: Add Docker official GPG key
-  apt_key:
+- name: Create directory for apt keyrings
+  file:
+    path: /etc/apt/keyrings
+    state: directory
+    mode: '0755'
+
+- name: Add Docker official GPG key (modern keyring approach)
+  get_url:
     url: https://download.docker.com/linux/debian/gpg
-    state: present
+    dest: /etc/apt/keyrings/docker.asc
+    mode: '0644'
 
 - name: Set up Docker repository for ARM architecture
   apt_repository:
-    repo: "deb [arch={{ 'arm64' if ansible_architecture == 'aarch64' else 'armhf' }}] https://download.docker.com/linux/debian {{ ansible_distribution_release }} stable"
+    repo: "deb [arch={{ 'arm64' if ansible_architecture == 'aarch64' else 'armhf' }} signed-by=/etc/apt/keyrings/docker.asc] https://download.docker.com/linux/debian {{ ansible_distribution_release }} stable"
     state: present
 
 - name: Install Docker Engine and CLI components