For each of the 34 roles (3 clients, 9 bots, 22 bridges), this commit:
- Adds `_restart_necessary: false` default variable
- Adds `register:` directives to config/image/systemd tasks
- Computes `_restart_necessary` via set_fact (OR of all .changed results)
- Wires `(_restart_necessary | bool)` in group_vars/matrix_servers
This allows the systemd service manager to skip unnecessary restarts
when running install-* tags and nothing actually changed.
Service roles and complex multi-service roles will follow separately.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Slavi Pantaleev