Add modular dev environment installer, dotfiles, and desnap script

Adds a TUI-driven, rollback-capable installer (install/install.sh +
install/modules/*.sh) covering JS/Python/systems toolchains, dev tooling,
browsers, chat apps, GNOME extras, and misc setup (wakatime key, ssh/gpg
perms, apt mirror benchmarking), all sourced from each vendor's official
install method. bootstrap.sh stows the zsh/git/tmux/vscode dotfiles and
runs the installer; desnap.sh purges snapd and replaces default snaps with
apt/Flatpak equivalents.

install/modules/postman.sh

@@ -0,0 +1,22 @@
+install_postman() {
+  if [[ -x /opt/Postman/Postman ]]; then ok "postman already installed"; return; fi
+
+  local tarball
+  tarball=$(mktemp --suffix=.tar.gz)
+  curl -fsSL https://dl.pstmn.io/download/latest/linux_64 -o "$tarball"
+  track_new_sudo_dir /opt/Postman
+  sudo tar -xzf "$tarball" -C /opt
+  rm -f "$tarball"
+  sudo ln -sf /opt/Postman/Postman /usr/local/bin/postman
+  rollback_push "sudo rm -f /usr/local/bin/postman /usr/share/applications/postman.desktop"
+
+  sudo tee /usr/share/applications/postman.desktop >/dev/null <<'EOF'
+[Desktop Entry]
+Name=Postman
+Exec=/opt/Postman/Postman %U
+Icon=/opt/Postman/app/resources/app/assets/icon.png
+Terminal=false
+Type=Application
+Categories=Development;
+EOF
+}