feat: add talks and series page types powered by a generalized archives layout

[nisrulz]

Summary

This PR generalizes the archives layout into a reusable grouped index and introduces two new page types on top of it: Talks and Series. It includes the layout changes, configuration, example content, and documentation across all four supported languages.

Changes

Core: generalized archives layout

• layouts/archives.html now renders any page set as a year- or month-grouped timeline (or flat list) instead of hardcoding the blog section.
• New group front matter options:
• group.section — which section to archive (defaults to the page's own section, falling back to params.archives.section)
• group.dateFormat — date format for list items
• group.groupBy — year (default), month, or none for a flat list
• Term pages (e.g. series) default to groupBy: none since they are already grouped by term.
• Extracted the archive list rendering into reusable partials: archive-item.html and grouped-list.html.

New page type: Talks

• A section such as talks is listed as a year-separated index by giving its _index.md the archives layout. No extra config needed.
• Example content in docs/content/talks/ demonstrates single-file posts and page-bundle posts.
• New Talks menu item added under the "More" menu.

New page type: Series

• New series taxonomy (configured alongside existing tag and category taxonomies).
• Posts tagged with a series term are grouped on an auto-generated /series// page.
• New navbar dropdown (type: series) lists all series automatically.
• Series links appear in the breadcrumb via GetTerms.
• Series _index.md term pages can set the title and enable the archives layout.
• Example content: two demo series (demo-series, hextra-tips) with posts.

Docs

• Rewrote docs/content/docs/advanced/additional-pages.* (en, fa, ja, zh-cn) to document the generalized archives layout, options, Talks, and Series setup.

Misc

• layouts/single.html now enables the breadcrumb for pages whose current section is not the site home.

Testing

Verified via the example site in docs/ — archives, /talks/, and /series/demo-series/ all render correctly in all four languages.

Screenshots

Series

Talks

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[nisrulz]

This was shown as high severity issue so I updated the dependency. I can revert it if this is useful for this PR. Please let me know.