Fix ansible-lint violations: FQCN, formatting, bugs, role renames

- Auto-fix FQCN, YAML formatting, jinja spacing, and free-form module
  syntax via ansible-lint --fix
- Fix comments misplaced inside module args by the auto-fixer
  (bluetooth-monitor, pi_standard_setup, pi_musicmouse)
- Fix notify: references left stale (lowercase) after handler names
  were re-cased, which would have silently broken reboot/restart
  handlers (pi_disable_onboard_bluetooth, pi_hifiberry_amp,
  pi_squeezelite, pi_standard_setup)
- Fix a task in pis/debmatic-install.yml missing its module name
  (apt_repository), which caused a real syntax-check failure
- Add missing play names, fix comment spacing, literal-compare idiom,
  and no-changed-when annotations
- Delete unused/broken roles/better-shell-env (unreferenced, invalid YAML)
- Rename all hyphenated role directories to underscore form to satisfy
  ansible-lint's role-name rule, updating every playbook/meta reference

Remaining lint findings (var-naming, package-latest, risky-file-permissions,
no-handler) intentionally left for follow-up per user decision.

roles/server_nfs/tasks/main.yml

@@ -0,0 +1,17 @@
+---
+- name: Apt install NFS server
+  ansible.builtin.apt:
+    name: nfs-kernel-server
+    update_cache: true
+- name: Ensure correct entry in /etc/exports
+  ansible.builtin.lineinfile:
+    path: /etc/exports
+    state: present
+    line: "{{ item }}"
+  with_items:
+    - "/data/main 192.168.178.0/255.255.255.0(rw,async,no_subtree_check)"
+- name: Restart nfs-kernel-server.service
+  ansible.builtin.systemd:
+    daemon_reload: true
+    state: started
+    name: nfs-kernel-server.service