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/00-base.sh

@@ -0,0 +1,9 @@
+install_00_base() {
+  if ! grep -qi ubuntu /etc/os-release 2>/dev/null; then
+    warn "this installer targets Ubuntu; continuing anyway"
+  fi
+  apt_install \
+    curl wget git ca-certificates gnupg lsb-release jq \
+    software-properties-common apt-transport-https \
+    build-essential unzip xz-utils stow
+}