PROJECT: Author and translator attribution across all themes

[mmcky]

Goal

Every QuantEcon theme should render author and translator attribution per lecture page, with the same data model and the same visual treatment, so that the translated editions (zh-cn, fa, fr, and future languages) have a consistent place to credit translators alongside the original authors.

Why

Today quantecon-book-theme has an authors option (a list of {name, url} pairs rendered per lecture) but no translator concept. quantecon-theme.mystmd and quantecon-sphinx-theme have neither. The translation programme (see QuantEcon/project-translation) is producing whole editions in other languages, and translator credit currently has nowhere to live in any of the themes. This surfaced in QuantEcon/quantecon-sphinx-theme#4 during the theme evaluation; this tracking issue widens it to a cross-theme feature.

Shared design decisions (settle here, implement in the sub-issues)

These should be decided once so the three implementations do not drift:

Question	Proposed default
Data model	Two lists, authors and translators, each a list of {name, url} pairs. Translators is optional and omitted on original-language editions.
Scope	Project-level config (html_theme_options / myst.yml site options) as the baseline, with optional per-page front matter that overrides the project value.
Placement	Directly under the page title, in the existing author slot where one exists. Footer placement can be a follow-up.
Labels	Localisable — the "Authors" / "Translators" labels must be overridable per edition so they render in the edition's language.
Markup	Use rel="author" and a distinct class for translators so the two are distinguishable in CSS and to crawlers.

Please push back on any of these in the comments; once agreed, the sub-issues implement them.

Sub-issues

• Add translator attribution alongside the existing authors option quantecon-book-theme#426 — extend the existing authors option with translators
• Add author and translator attribution per lecture page quantecon-theme.mystmd#143 — add authors and translators rendering
• No support for Authors and Translator attribution per lecture quantecon-sphinx-theme#4 — add authors and translators (neither exists today)

Follow-ups once the themes ship

• Roll out translators config to the translated lecture repos (zh-cn, fa, fr editions).
• Document the option in QuantEcon.manual alongside the other theme options.