feat: [US-004] Add SSH tunnel auto-start for Windows services

- Add ssh-tunnel.ps1: Windows SSH tunnel manager (equivalent to ssh-tunnel.sh)
  - Supports password auth via plink.exe (PuTTY)
  - Supports ssh_hostkey for non-interactive batch mode
  - Commands: start, stop, restart, status

- Add start-backend-service.ps1: NSSM service wrapper
  - Starts SSH tunnels before uvicorn
  - Waits for tunnel ports to be accessible (30s timeout)
  - Configured by Install-ROA2WEB.ps1

- Add start.ps1: Windows equivalent of start.sh
  - Orchestrates SSH tunnel + backend + frontend startup

- Add backend/shared/ssh_tunnel_manager.py: Python monitoring
  - Background asyncio task monitors tunnel health every 30s
  - Auto-restarts tunnels after 2 consecutive failures
  - Exposes status to /health endpoint

- Update ROA2WEB-Console.ps1:
  - Add Deploy-Scripts function
  - Update Update-ServiceToUseVenv to use wrapper script

- Fix PowerShell reserved variable ($PID -> $tunnelPid)
- Fix script path detection (scripts/ vs deployment/windows/scripts/)
- Update README.md with ssh_hostkey documentation

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

deployment/linux/deploy.sh

@@ -205,6 +205,8 @@ create_package() {
         "ROA2WEB-Console.ps1"
         "Install-ROA2WEB.ps1"
         "Check-And-Deploy.ps1"
+        "ssh-tunnel.ps1"
+        "start-backend-service.ps1"
     )
 
     for script in "${SCRIPTS[@]}"; do