Add English translations for all 379 recipe and tip files

Use dotlang AI translation (aiursoft-instruct:latest via Ollama) to
translate all Chinese content to English under en/ subfolder:
- en/dishes/: all recipe categories (aquatic, breakfast, condiment,
  dessert, drink, meat_dish, semi-finished, soup, staple, vegetable_dish)
- en/tips/: learn/ and advanced/ cooking guides
- en/README.md, en/CONTRIBUTING.md, en/CODE_OF_CONDUCT.md

The mkdocs-static-i18n plugin (docs_structure: folder) serves Chinese
at the root and English at /en/, with a language switcher in the UI.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>