Add auto-install for missing prerequisites

- New lib/prereqs.sh: detects distro (Arch, Debian/Ubuntu, RHEL/Fedora,
  openSUSE) and installs git + podman/docker if missing
- Podman preferred over docker; user chooses if neither present
- Docker install also enables systemd service and adds user to docker group
- README updated: prereqs table now shows auto-install support

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

wizard.sh

@@ -7,25 +7,11 @@ set -euo pipefail
 WIZARD_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 
 source "$WIZARD_DIR/lib/utils.sh"
+source "$WIZARD_DIR/lib/prereqs.sh"
 source "$WIZARD_DIR/lib/core.sh"
 source "$WIZARD_DIR/lib/project.sh"
 source "$WIZARD_DIR/lib/workflow.sh"
 
-# ── Prerequisites ──────────────────────────────────────────────────────────
-check_prerequisites() {
-    header "Checking Prerequisites"
-    require_cmd git
-    if command -v docker &>/dev/null; then
-        CONTAINER_CMD="docker"
-    elif command -v podman &>/dev/null; then
-        CONTAINER_CMD="podman"
-    else
-        die "Neither docker nor podman found. Install one to use devcontainers."
-    fi
-    success "git: $(git --version)"
-    success "$CONTAINER_CMD: $($CONTAINER_CMD --version | head -1)"
-}
-
 # ── Project info ───────────────────────────────────────────────────────────
 collect_project_info() {
     header "Project Details"