feat(samba_server): new role for SMB/CIFS shares

Mirrors the nfs_server design: standalone tdbsam server, per-share access
control (valid_users, write_list, force_user/group), optional guest fallback
(map to guest = Bad User), UFW rules for ports 445/139, testparm-validated
config, idempotent smbpasswd user creation.

roles/samba_server/handlers/main.yml

@@ -0,0 +1,6 @@
+---
+- name: Restart samba
+  ansible.builtin.systemd:
+    name: "{{ samba_service_name }}"
+    state: restarted
+    daemon_reload: true