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/node.sh

@@ -0,0 +1,12 @@
+install_node() {
+  export NVM_DIR="$HOME/.nvm"
+  if [[ ! -s "$NVM_DIR/nvm.sh" ]]; then
+    err "nvm not found; run the nvm module first"
+    return 1
+  fi
+  # shellcheck disable=SC1091
+  \. "$NVM_DIR/nvm.sh"
+
+  nvm install --lts
+  nvm alias default 'lts/*'
+}