Add Ansible playbook to configure PiKVM

Add Nix shell to flake
Monitor PiKVM with Prometheus
Serve Prometheus on /

ansible/ansible.cfg

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+[defaults]
+inventory = inventory
+remote_tmp = /tmp/ansible
+ansible_python_interpreter = /usr/bin/python3.12

ansible/inventory/pikvm.yml

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+all:
+  hosts:
+    pikvm:
+      ansible_host: pikvm.dmz
+      ansible_user: root

ansible/main.yml

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+---
+- name: Configure PiKVM server
+  hosts: all
+
+  roles:
+    - pikvm

ansible/roles/pikvm/tasks/main.yml

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+---
+- name: Mount filesystem as read-write
+  ansible.builtin.command: rw
+  vars:
+    root_mount: "{{ ansible_mounts | selectattr('mount', 'equalto', '/') | first }}"
+  when: "'ro' in root_mount.options.split(',')"
+
+- name: Install Tailscale
+  community.general.pacman:
+    name: tailscale-pikvm
+    state: latest
+
+- name: Enable Tailscale
+  ansible.builtin.systemd_service:
+    name: tailscaled
+    state: started
+    enabled: true
+
+- name: Mount filesystem as read-only
+  ansible.builtin.command: ro