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/pnpm.sh

@@ -0,0 +1,7 @@
+install_pnpm() {
+  if has_cmd pnpm; then ok "pnpm already installed"; return; fi
+  track_new_dir "$HOME/.local/share/pnpm"
+  curl -fsSL https://get.pnpm.io/install.sh | sh -
+  profile_add 'export PNPM_HOME="$HOME/.local/share/pnpm"'
+  profile_add 'case ":$PATH:" in *":$PNPM_HOME:"*) ;; *) export PATH="$PNPM_HOME:$PATH" ;; esac'
+}