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/git.sh

@@ -0,0 +1,20 @@
+#!/bin/bash
+# Step 8: Git + Lazygit
+
+step "8/9 — Setting up Git + Lazygit"
+
+if ! command -v lazygit &>/dev/null; then
+  if $IS_ARCH; then
+    $PKG_INSTALL lazygit
+  else
+    LAZYGIT_VERSION=$(curl -ks "https://api.github.com/repos/jesseduffield/lazygit/releases/latest" | jq -r '.tag_name' | sed 's/v//')
+    curl -kLo /tmp/lazygit.tar.gz "https://github.com/jesseduffield/lazygit/releases/latest/download/lazygit_${LAZYGIT_VERSION}_Linux_x86_64.tar.gz"
+    tar xf /tmp/lazygit.tar.gz -C /tmp lazygit
+    sudo mv /tmp/lazygit /usr/local/bin/
+  fi
+fi
+info "Lazygit installed"
+
+mkdir -p ~/.config/lazygit
+write_lazygit_config ~/.config/lazygit/config.yml
+info "Lazygit configured with $THEME_DISPLAY_NAME"