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/pyenv.sh

@@ -0,0 +1,16 @@
+install_pyenv() {
+  apt_install make build-essential libssl-dev zlib1g-dev libbz2-dev \
+    libreadline-dev libsqlite3-dev wget curl llvm libncursesw5-dev \
+    xz-utils tk-dev libxml2-dev libxmlsec1-dev libffi-dev liblzma-dev
+
+  if [[ -d "$HOME/.pyenv" ]]; then
+    ok "pyenv already installed"
+  else
+    track_new_dir "$HOME/.pyenv"
+    curl -fsSL https://pyenv.run | bash
+  fi
+
+  profile_add 'export PYENV_ROOT="$HOME/.pyenv"'
+  profile_add 'export PATH="$PYENV_ROOT/bin:$PATH"'
+  profile_add 'eval "$(pyenv init - zsh)"'
+}