No support for Authors and Translator attribution per lecture

The theme has no equivalent of quantecon-book-theme's authors option, and no notion of translators at all. Raised during the theme evaluation in QuantEcon/lecture-python-programming#475 (closed, never merged).

How this surfaced. Porting the QuantEcon Python Programming lecture config to this theme meant deleting the authors block outright, because there was nothing to map it onto:

What's wanted. Author and translator attribution rendered per lecture page. Translators matter specifically because the QuantEcon lecture series are translated into several languages (zh-cn, fa, fr), and translator credit currently has nowhere to live in either theme.

Design questions worth settling first

• Is attribution per-page (front-matter driven) or per-project (html_theme_options driven), or both, with page-level overriding project-level?
• Where does it render — under the page title, in the footer, or both?
• Does this belong in a brand-neutral theme at all, or is it QuantEcon-specific? PLAN.md positions this theme as deliberately brand-neutral with "minimal opinion", but per-page authorship is a general scholarly-documentation need, not a QuantEcon one. Worth deciding explicitly rather than by default.
• If it lands here, does quantecon-book-theme eventually inherit it, per the PLAN.md goal of this theme becoming the upstream base?

Start with PLAN.md and the existing theme configuration and lecture-page rendering paths. Resolve whether attribution is page-level, project-level, or both, where it renders, and whether it belongs in this brand-neutral theme. Done means the scope and rendering design are agreed before implementation begins.