feat(rego-tunnel): Add Dockerfile and build scripts for cisco-vpn image

Includes:
- Dockerfile for native Cisco Secure Client in Docker
- Build scripts (init-vpn.sh, startup-vnc.sh, vpn-connect.sh)
- VNC configuration (xstartup, vnc.service)
- build.sh for manual image builds
- README documenting the architecture

Note: cisco-secure-client-full.tar.gz is gitignored (large binary)
Copy it from ~/projects/cisco-vpn/build/ before building.

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

apps/rego-tunnel/build/scripts/vnc.service

@@ -0,0 +1,14 @@
+[Unit]
+Description=VNC and noVNC Server
+After=network.target vpnagentd.service
+
+[Service]
+Type=simple
+ExecStart=/opt/scripts/startup-vnc.sh
+Restart=always
+RestartSec=5
+Environment=HOME=/root
+Environment=USER=root
+
+[Install]
+WantedBy=multi-user.target