Flyer library pattern

- Use `FlyerLibrarySection` for undated, non-news awareness/informational flyers (foster recruitment, volunteer recruitment, spay/neuter awareness, safety education).

- Never combine flyer content with `EventsNewsSection`'s dated event/news data — a flyer belongs here specifically because it has no date or venue.

- `category` is required on every `FlyerLibraryItem` so filter pills stay meaningful; an uncategorized flyer would otherwise be unreachable in a filtered view.

- Core flyer images render via anchor + `img`, so browsing works without JavaScript.

- Category filter pills and the lightbox are optional progressive enhancements, not the primary access path.

- Download uses a plain `<a download>` link, not the Printable Material Module's print layout — flyers are pre-made images, not generated documents.

- Use `categoryFilter` to lock the section to a single category and hide the pills, for embedding a filtered teaser on another page (e.g. a foster flyer on the Foster page).

- Defaults: `columns=3`, `showFilters=true`, `enableLightbox=true`.

- Live example: Flyer library example page

- Component: `template/src/components/patterns/FlyerLibrarySection.tsx`