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/docker.sh

@@ -0,0 +1,20 @@
+install_docker() {
+  if has_cmd docker; then ok "docker already installed"; return; fi
+  apt_install ca-certificates curl
+
+  local codename
+  codename=$(ubuntu_codename)
+  if ! curl -fsSL -o /dev/null "https://download.docker.com/linux/ubuntu/dists/${codename}/Release"; then
+    warn "Docker has no repo for '${codename}' yet, falling back to 'noble' (24.04)"
+    codename=noble
+  fi
+
+  apt_add_repo docker /etc/apt/keyrings/docker.asc \
+    https://download.docker.com/linux/ubuntu/gpg \
+    "deb [arch=$(deb_arch) signed-by=/etc/apt/keyrings/docker.asc] https://download.docker.com/linux/ubuntu ${codename} stable"
+  apt_install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin
+
+  sudo usermod -aG docker "$USER"
+  rollback_push "sudo gpasswd -d '$USER' docker"
+  warn "log out/in (or run 'newgrp docker') for docker group membership to take effect"
+}