This fixes two bugs that prevented temperature monitoring from working
after running install-sensor-proxy.sh on LXC deployments:
1. CRITICAL: Pulse service not restarted after systemd override
- The installer wrote PULSE_SENSOR_PROXY_SOCKET env var to systemd
drop-in and ran daemon-reload, but never restarted Pulse service
- Running Pulse instances continued using old environment variables
- Temperatures wouldn't work until manual Pulse restart
- Now: Automatically restart Pulse if running after writing override
2. Added guard to check if Pulse service exists before configuring
- Installer would write systemd override even if Pulse not installed
- Left orphaned drop-in files that confused users
- Now: Check if pulse.service exists, warn and skip if not found
3. MINOR: Fix inconsistent Docker mount instructions
- docker-compose.yml showed :ro (read-only) mount
- Installer output showed :rw (read-write) mount
- Changed installer to match compose file (:ro is correct and secure)
Impact: Users in #600 reported "socketFound=false" even after running
installer successfully. This was because Pulse never picked up the new
socket path without a restart.