Add OpenSnitch application firewall installation for Linux

[Copilot]

This PR adds support for installing OpenSnitch, a GNU/Linux interactive application firewall, as part of the dotfiles installation process.

Changes Made

• Added script/install.d/82-opensnitch.sh: New installation script that:

  • Downloads and installs OpenSnitch daemon and UI packages from GitHub releases
  • Uses the latest stable version (v1.7.0.0) with fallback support
  • Follows existing repository patterns (OS detection, command checking, numbered naming)
  • Enables and starts the OpenSnitch systemd service
  • Linux-only installation (gracefully skips on other platforms)

• Updated tests/test_binaries.py: Added opensnitchd and opensnitch-ui to the test binaries list with Linux-only conditional checks

Features

OpenSnitch provides:

• Interactive outbound connection filtering
• System-wide ad, tracker, and malware domain blocking
• System firewall configuration from GUI (nftables)
• Multi-node management from centralized GUI
• SIEM integration capabilities

Installation Details

The script downloads the official .deb packages for both the daemon (opensnitchd) and UI (opensnitch-ui) components, installs them via apt, and ensures the service is properly configured and running.

Tested on Ubuntu 24.04 - installation completes successfully and both binaries are available in PATH.

Fixes #16.

Warning

Firewall rules blocked me from connecting to one or more addresses

I tried to connect to the following addresses, but was blocked by firewall rules:

• api.github.com
  • Triggering command: curl -s REDACTED (dns block)
  • Triggering command: curl -s -I REDACTED (dns block)
• esm.ubuntu.com
  • Triggering command: /usr/lib/apt/methods/https (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to my firewall allow list

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