Addresses #528
Introduces pulse-temp-proxy architecture to eliminate SSH key exposure in containers:
**Architecture:**
- pulse-temp-proxy runs on Proxmox host (outside LXC/Docker)
- SSH keys stored on host filesystem (/var/lib/pulse-temp-proxy/ssh/)
- Pulse communicates via unix socket (bind-mounted into container)
- Proxy handles cluster discovery, key rollout, and temperature fetching
**Components:**
- cmd/pulse-temp-proxy: Standalone Go binary with unix socket RPC server
- internal/tempproxy: Client library for Pulse backend
- scripts/install-temp-proxy.sh: Idempotent installer for existing deployments
- scripts/pulse-temp-proxy.service: Systemd service for proxy
**Integration:**
- Pulse automatically detects and uses proxy when socket exists
- Falls back to direct SSH for native installations
- Installer automatically configures proxy for new LXC deployments
- Existing LXC users can upgrade by running install-temp-proxy.sh
**Security improvements:**
- Container compromise no longer exposes SSH keys
- SSH keys never enter container filesystem
- Maintains forced command restrictions
- Transparent to users - no workflow changes
**Documentation:**
- Updated TEMPERATURE_MONITORING.md with new architecture
- Added verification steps and upgrade instructions
- Preserved legacy documentation for native installs
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