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_basic_environment/README.md

@@ -0,0 +1,3 @@
+# server_basic_environment
+
+apt update/upgrade, plus downloads and installs `mbenv` on the server.

roles/server_basic_environment/tasks/main.yml

@@ -0,0 +1,23 @@
+---
+- name: Do apt update/upgrade
+  ansible.builtin.apt:
+    upgrade: "yes"
+    update_cache: "yes"
+    cache_valid_time: "300"
+- name: Apt install download & unzip packages
+  ansible.builtin.apt:
+    name:
+      - wget
+      - zip
+      - htop
+      - xz-utils
+      - python3
+      - python3-venv
+      - python3-wheel
+      - git
+      - iotop
+- name: Download and install mbenv
+  ansible.builtin.unarchive:
+    src: "https://owncloud.bauer.tech/s/vMu7X4mRl2vComu/download?path=%2F&files=mbenv.tar.xz"
+    remote_src: true
+    dest: "/home/core/"