refactor(k3s): centralize k3s primary server IP and integrate Netcup DNS

Signed-off-by: Tuan-Dat Tran <tuan-dat.tran@tudattr.dev>

playbooks/k3s-storage.yml

@@ -1,8 +1,6 @@
 - name: Set up storage
   hosts: k3s_nodes
   gather_facts: true
-  vars:
-    k3s_primary_server_ip: "{{ groups['k3s_server'] | map('extract', hostvars, 'ansible_host') | list | first }}"
   pre_tasks:
     - name: Get K3s token from the first server
       when: host.ip == k3s_primary_server_ip and inventory_hostname in groups["k3s_server"]