Extend dots.ports module to remaining NixOS hosts

[genebean]

Summary

• hetznix02: import shared ports module, replace hardcoded allowedTCPPorts list with lib.pipe-derived firewall (22/80/443 come from shared), wire node-exporter and nginx-exporter port references in monitoring.nix
• kiosk-entryway: import shared ports module, wire node-exporter port in monitoring.nix
• kiosk-gene-desk: import shared ports module, make node-exporter port explicit via inherit
• bigboy, rainbow-planet: import shared ports module for consistency; no service ports to wire

Test plan

• nixos-rebuild dry-activate on hetznix02 — verify firewall still opens 22/80/443
• nixos-rebuild dry-activate on kiosk-entryway and kiosk-gene-desk
• Confirm node-exporter and nginx-exporter still scrape correctly on hetznix02

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