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/spotify.sh

@@ -0,0 +1,7 @@
+install_spotify() {
+  if has_cmd spotify; then ok "spotify already installed"; return; fi
+  apt_add_repo spotify /etc/apt/trusted.gpg.d/spotify.gpg \
+    https://download.spotify.com/debian/pubkey_6224F9941A8AA6D1.gpg \
+    "deb http://repository.spotify.com stable non-free"
+  apt_install spotify-client
+}