5-minute health monitoring for all 4 machines + Gitea:
- SSH connectivity check (socket-based, instant)
- Service check via SSH (nginx, gitea, hermes-agent, evennia)
- Disk usage check on all machines
- Local process check (hermes, ollama, openclaw, evennia)
- Telegram alert with 1-hour cooldown per alert
- Running uptime stats saved to ~/.local/timmy/fleet-health/uptime.json
- Per-day log files
Fixes timmy-home#555, FLEET-006
