Add Docsify docs server with nginx

Move docs into docs/ directory, add Docsify for markdown rendering.
Standalone Docker stack (nginx:alpine) on port 8090.
wiring.html served as native HTML with correct MIME type.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/_sidebar.md

@@ -0,0 +1,4 @@
+- [Главная](/)
+- [Спецификация](spec.md)
+- [История изменений](changelog.md)
+- [Схема подключения](wiring.html ':ignore')