Restore Homebrew and Debian package manager support

- Add Homebrew formula (brew_dist/archivebox.rb) using virtualenv pattern
  with auto-generation via homebrew-pypi-poet in bin/build_brew.sh
- Add Debian packaging via nFPM (pkg/debian/) with thin .deb that pip-installs
  archivebox into /opt/archivebox/venv on postinstall
- Add build/release scripts: bin/{build,release}_{brew,deb}.sh
- Update CI workflows to build packages on release and test them
- Update README apt/brew install instructions with working commands
- Update bin/setup.sh to use .deb download instead of old Launchpad PPA

https://claude.ai/code/session_01Vx1EsNrNySgsc8Y67dGzCn

brew_dist/archivebox.rb

@@ -0,0 +1,51 @@
+# This formula is auto-generated by bin/build_brew.sh using homebrew-pypi-poet.
+# To update: run bin/build_brew.sh, or trigger the GitHub Actions homebrew workflow.
+#
+# Users install with:
+#   brew tap archivebox/archivebox
+#   brew install archivebox
+
+class Archivebox < Formula
+  include Language::Python::Virtualenv
+
+  desc "Self-hosted internet archiving solution"
+  homepage "https://github.com/ArchiveBox/ArchiveBox"
+  url "https://files.pythonhosted.org/packages/source/a/archivebox/archivebox-0.9.3.tar.gz"
+  sha256 "" # auto-filled by bin/build_brew.sh
+  license "MIT"
+  head "https://github.com/ArchiveBox/ArchiveBox.git", branch: "dev"
+
+  depends_on "python@3.13"
+  depends_on "node"
+  depends_on "git"
+  depends_on "wget"
+  depends_on "curl"
+  depends_on "ripgrep"
+  depends_on "yt-dlp"
+
+  # Python dependency resource blocks are auto-generated by bin/build_brew.sh
+  # using homebrew-pypi-poet. Run that script to populate this section.
+  # AUTOGENERATED_RESOURCES_START
+  # AUTOGENERATED_RESOURCES_END
+
+  def install
+    virtualenv_install_with_resources
+  end
+
+  def post_install
+    # Install runtime dependencies (plugins, JS extractors, etc.)
+    system bin/"archivebox", "install", "--binproviders", "pip,npm"
+  end
+
+  service do
+    run [opt_bin/"archivebox", "server", "--quick-init", "0.0.0.0:8000"]
+    keep_alive crashed: true
+    working_dir var/"archivebox"
+    log_path var/"log/archivebox.log"
+    error_log_path var/"log/archivebox.log"
+  end
+
+  test do
+    assert_match version.to_s, shell_output("#{bin}/archivebox version")
+  end
+end