Function render_nav 

pub fn render_nav(
    items: &[NavItem],
    current_path: &str,
    pages: &[Page],
    show_all_photos: bool,
) -> Markup

Renders the navigation menu (hamburger style, slides from right).

Albums are listed first, then a separator, then pages (numbered pages only). Link pages render as direct external links; content pages link to /{slug}.html.

When show_all_photos is true, an “All Photos” item is appended after the album list — it points at /all-photos/ which is rendered only when [full_index] generates = true.