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_standard_setup/defaults/main.yml

@@ -1,11 +1,11 @@
 ---
-wifi_ssid: "" # put SSID here to configure wifi
+pi_standard_setup_wifi_ssid: "" # put SSID here to configure wifi
 ansible_user: "root" # "User to connect with, put in 'pi' here if you connect the first time, else leave empty"
-new_hostname: "" # set this to change the hostname
+pi_standard_setup_new_hostname: "" # set this to change the hostname
 
-timezone: "Europe/Berlin"
-wifi_country: "DE"
-wifi_pass_url: "bauer_wifi" # has to be in keepass with url "wifi_pass_url"
+pi_standard_setup_timezone: "Europe/Berlin"
+pi_standard_setup_wifi_country: "DE"
+pi_standard_setup_wifi_pass_url: "bauer_wifi" # has to be in keepass with url "wifi_pass_url"
 ansible_ssh_pass: "raspberry"
 ansible_become_password: "raspberry"
 ansible_become: true