Fix remaining ansible-lint violations: file permissions, var-naming, package pinning

- risky-file-permissions (32): add explicit mode: to copy/template/file tasks,
  matching the umask-derived permissions they already had (0644 for configs
  and systemd units, 0755 for created directories) — no functional change.
- var-naming (28): prefix role-scoped vars with their role name across
  pi_dhtsensor, pi_dhtsensor_circuitpython, pi_shairport, pi_squeezelite,
  pi_squeezelite_custom, pi_sispmctl, pi_standard_setup, and pi_sysdweb's
  sysdweb_name (shared by 9 consuming roles). Updated every dependent
  template, task reference, and matching inventory.yml override, and
  verified resolved values with ansible-inventory before/after.
- Fixes a latent bug found while renaming: pi_standard_setup's "Get/Change
  WiFi country" tasks reused the name wifi_country for both the role default
  and a register, so the register silently clobbered the default before
  do_wifi_country ever read it. Split into distinct names so the intended
  default value is used.
- package-latest (2): pin docker-ce/docker-compose-plugin installs in
  server_debian_docker to state: present.
- no-handler (1): move pi_lirc's "Reboot if boot overlay changed" into a
  proper handler notified by the boot-overlay task.

ansible-lint now passes clean at the production profile.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

roles/pi_musicmouse/tasks/main.yml

@@ -21,14 +21,17 @@
   ansible.builtin.file:
     path: /media/musicmouse
     state: directory
+    mode: "0755"
 - name: Install config file
   ansible.builtin.copy:
     src: config.yml
     dest: /media/musicmouse/config.yml
+    mode: "0644"
 - name: Install systemd service file
   ansible.builtin.copy:
     src: musicmouse.service
     dest: /etc/systemd/system/
+    mode: "0644"
 - name: Add script to autostart and start now
   ansible.builtin.systemd:
     name: musicmouse
@@ -39,6 +42,7 @@
   ansible.builtin.copy:
     src: smb.conf
     dest: /etc/samba/
+    mode: "0644"
 - name: Restart samba
   ansible.builtin.systemd:
     name: smbd