fix: allow images in list summary cards (#971)

## Summary

Lets list pages opt in to image summary cards, and makes published dates
consistent across single pages and summary cards.

- Adds an opt-in `params.ananke.pages.show_list_images` switch. When
enabled, list pages render the existing `summary-with-image` card
instead of the plain `summary` card. Default is off, so existing sites
are unchanged.
- Applies the existing `params.ananke.pages.show_date` setting (with the
per-page `ananke.show_date` override) to summary cards so dates display
consistently with single pages.
- Extracts the shared date-visibility logic — previously duplicated in
`single.html` — into a single `layouts/_partials/func/ShowDate.html`
partial used by `single.html`, `summary.html`,
`summary-with-image.html`, and `post/summary.html`.

Closes #217.

## Documentation

Documentation PR: gohugo-ananke/documentation#13

## Scope notes

- Taxonomy term pages (e.g. `/tags/foo/`) are list pages that fall back
to `list.html`, so they pick up image cards from the same switch — no
separate template change needed.
- `summary-with-image` is also used by the home page recent-posts
section, so enabling dates means those cards now show dates by default
(controllable via `show_date`). This is intentional and documented, but
it is a visible default change worth a maintainer's eye before merge.

## Testing

Adds a phase to `scripts/test-hugo-quickstart.ts` that builds a content
section twice:

1. Defaults — asserts no image cards and that dates show.
2. `show_list_images = true` + `show_date = false` — asserts image cards
render and dates are hidden, proving the two settings are independent.

Verified manually that:

- Image cards appear on section lists and taxonomy term lists when
enabled, and never by default.
- Dates show by default and respect `ananke.pages.show_date = false`
plus the per-page `ananke.show_date = true` opt-back-in, on both summary
cards and single pages.
- `single.html` output is unchanged by the partial extraction.
- The new assertions fail if the image switch or the date logic
regresses.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>