refactor(proxmox_lxc_provision): centralize module_defaults so tasks_from works without setup

Previously the community.proxmox.proxmox / proxmox_vm_info module_defaults
were defined inline on the outer block in main.yml. Invoking individual
task files via 'tasks_from: stop' (or delete/convert/etc.) bypassed
main.yml, leaving the API parameters unset and producing
'missing required arguments: api_host, api_user' errors. The README
worked around this by telling callers to repeat the module_defaults
block at the play level — easy to forget, and duplicated config.

Extract the defaults dict into _proxmox_module_defaults in
defaults/main.yml (using a YAML anchor to share between the two
modules), and wrap every task file that calls a Proxmox module in a
block that references it. Callers only need the proxmox_* connection
vars in scope (typically group_vars/all/) — both 'roles:' and
'tasks_from:' invocations now configure the API consistently.

Files wrapped: check-exists, create, clone, update, start, stop,
delete, convert. wait/post-clone/edit-config don't call Proxmox modules
and are unchanged. main.yml's now-redundant outer module_defaults is
removed.

README updated to drop the 'Using Standalone Tasks' workaround
boilerplate.

roles/proxmox_lxc_provision/tasks/main.yml

@@ -1,63 +1,51 @@
 ---
-- name: Proxmox LXC provision
-  module_defaults:
-    community.proxmox.proxmox: &proxmox_defaults
-      api_host: "{{ proxmox_api_host }}"
-      api_port: "{{ proxmox_api_port }}"
-      api_user: "{{ proxmox_api_user }}"
-      api_token_id: "{{ proxmox_api_token_id }}"
-      api_token_secret: "{{ proxmox_api_token_secret }}"
-      validate_certs: "{{ proxmox_api_validate_certs }}"
-      node: "{{ proxmox_node }}"
-    community.proxmox.proxmox_vm_info: *proxmox_defaults
+- name: Check if container exists
+  ansible.builtin.include_tasks:
+    file: check-exists.yml
+
+- name: Skip if container already exists
+  meta: end_host
+  when: lxc_exists | bool
+
+- name: Container source must be defined (lxc_clone_from or lxc_template)
+  ansible.builtin.fail:
+    msg: "Neither lxc_clone_from or lxc_template are defined"
+  when: lxc_clone_from is undefined and lxc_template is undefined
+
+- name: Clone container from another container or template, then update
+  when: lxc_clone_from is defined
   block:
-    - name: Check if container exists
+    - name: Clone from template
       ansible.builtin.include_tasks:
-        file: check-exists.yml
+        file: clone.yml
+      register: clone_result
 
-    - name: Skip if container already exists
-      meta: end_host
-      when: lxc_exists | bool
-
-    - name: Container source must be defined (lxc_clone_from or lxc_template)
-      ansible.builtin.fail:
-        msg: "Neither lxc_clone_from or lxc_template are defined"
-      when: lxc_clone_from is undefined and lxc_template is undefined
-
-    - name: Clone container from another container or template, then update
-      when: lxc_clone_from is defined
-      block:
-        - name: Clone from template
-          ansible.builtin.include_tasks:
-            file: clone.yml
-          register: clone_result
-
-        - name: Update container
-          ansible.builtin.include_tasks:
-            file: update.yml
-          vars:
-            lxc_vmid: "{{ clone_result.vmid }}"
-          register: lxc_result
-
-    - name: Create the new container
+    - name: Update container
       ansible.builtin.include_tasks:
-        file: create.yml
-      when: lxc_template is defined and lxc_clone_from is undefined
-
-    - name: Start the created container and wait for ssh
+        file: update.yml
       vars:
-        lxc_vmid: "{{ lxc_result.vmid }}"
-      ansible.builtin.include_tasks:
-        file: "{{ item }}"
-      loop:
-        - start.yml
-        - wait.yml
-      when: lxc_start
+        lxc_vmid: "{{ clone_result.vmid }}"
+      register: lxc_result
 
-    - name: Post clone updates
-      when: lxc_clone_from is defined
-      delegate_to: "{{ lxc_hostname }}"
-      block:
-        - name: Include post-clone tasks
-          ansible.builtin.include_tasks:
-            file: post-clone.yml
+- name: Create the new container
+  ansible.builtin.include_tasks:
+    file: create.yml
+  when: lxc_template is defined and lxc_clone_from is undefined
+
+- name: Start the created container and wait for ssh
+  vars:
+    lxc_vmid: "{{ lxc_result.vmid }}"
+  ansible.builtin.include_tasks:
+    file: "{{ item }}"
+  loop:
+    - start.yml
+    - wait.yml
+  when: lxc_start
+
+- name: Post clone updates
+  when: lxc_clone_from is defined
+  delegate_to: "{{ lxc_hostname }}"
+  block:
+    - name: Include post-clone tasks
+      ansible.builtin.include_tasks:
+        file: post-clone.yml