refactor: update README and templates for improved backup configuration and logging

Co-authored-by: Copilot <copilot@github.com>

tasks/install.yml

@@ -1,7 +1,10 @@
 ---
 - name: proxmox backup client | get GPG key
-  apt_key:
+  get_url:
     url: "{{ pbs_repo_key }}"
+    dest: /etc/apt/trusted.gpg.d/proxmox-release-bookworm.gpg
+    mode: '0644'
+  become: yes
 
 - name: proxmox backup client | add repository
   become: yes