refactor: use module_defaults for proxmox API connection

- Replace YAML merge keys (<<:) with module_defaults block in main.yml
- Simplify connection variables to individual vars instead of dictionary
- Remove redundant connection params from individual task files
- Document standalone task usage requires play-level module_defaults
- Update README examples with new variable pattern

roles/proxmox_lxc_provision/tasks/clone.yml

@@ -1,7 +1,6 @@
 ---
 - name: Create a full clone of the container
   community.general.proxmox:
-    <<: "{{ proxmox_api_connection }}"
     vmid: "{{ lxc_vmid | default(0) }}"
     clone: "{{ lxc_clone_from }}"
     clone_type: "{{ lxc_clone_type }}"
@@ -23,7 +22,7 @@
   become: yes
   register: resize_result
   changed_when: resize_result.rc == 0 and 'already at specified size' not in resize_result.stderr
-  failed_when: 
+  failed_when:
     - resize_result.rc != 0
     - "'already at specified size' not in resize_result.stderr"
   when: lxc_size is defined