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/bun.sh

@@ -0,0 +1,7 @@
+install_bun() {
+  if has_cmd bun; then ok "bun already installed"; return; fi
+  track_new_dir "$HOME/.bun"
+  NO_MODIFY_PATH=1 bash -c "$(curl -fsSL https://bun.sh/install)"
+  profile_add 'export BUN_INSTALL="$HOME/.bun"'
+  profile_add 'export PATH="$BUN_INSTALL/bin:$PATH"'
+}