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.

server.yml

@@ -1,10 +1,10 @@
-
-- hosts: server
+---
+- name: Server
+  hosts: server
   roles:
-    - server-basic-environment
-    - server-debian-docker
-    - server-exthdd-mount
-    - server-nfs
-    #- server-link-aggregation
-    #- bluetooth-monitor
-
+    - server_basic_environment
+    - server_debian_docker
+    - server_exthdd_mount
+    - server_nfs
+    # - server_link_aggregation
+    # - bluetooth_monitor