refactor: restructure installation to modular architecture

- Remove monolithic bootstrap.sh in favor of modular design
- Add install.sh as new main entry point with improved UX
- Split functionality into focused modules:
  - lib/common.sh: shared utilities and environment detection
  - lib/packages.sh: base system packages
  - lib/neovim.sh: Neovim and LazyVim setup
  - lib/arduino.sh: Arduino CLI and board cores
  - lib/git.sh: Git and Lazygit configuration
  - lib/shell-config.sh: Zsh and shell environment
  - lib/starship.sh: Starship prompt setup
  - lib/zellij.sh: Zellij terminal multiplexer
  - lib/scaffold.sh: project scaffolding utilities
- Update README with new installation instructions and architecture
- Improve error handling and user feedback across modules
- Maintain compatibility with both Arch Linux and Ubuntu/WSL2

This modular approach enables better maintainability, testing,
and allows users to selectively run components as needed.

lib/packages.sh

@@ -0,0 +1,23 @@
+#!/bin/bash
+# Step 1: Base packages
+
+step "1/9 — Installing base packages"
+
+if $IS_ARCH; then
+  sudo pacman -Syu --noconfirm
+  $PKG_INSTALL base-devel git curl unzip wget ripgrep fd bat eza tree jq zsh clang
+  # tio is in AUR — install yay if needed, then tio
+  if ! command -v yay &>/dev/null; then
+    info "Installing yay (AUR helper)..."
+    git clone https://aur.archlinux.org/yay.git /tmp/yay
+    (cd /tmp/yay && makepkg -si --noconfirm)
+    rm -rf /tmp/yay
+  fi
+  yay -S --needed --noconfirm tio
+else
+  sudo apt update && sudo apt upgrade -y
+  $PKG_INSTALL build-essential git curl unzip wget ripgrep bat eza tree jq zsh clang-format tio
+  # fd is named differently on Ubuntu
+  sudo apt install -y fd-find 2>/dev/null || true
+fi
+info "Base packages installed"