fix(web): localize repo pages and share UI

[bpetrynski]

Summary

• localize repo navigation, document fallbacks, share dialogs, and language filters so the repo UI follows the selected app locale
• replace hardcoded Chinese repo-page strings with locale-aware English/Chinese copy and add the missing Polish option in the repository submit flow
• simplify repo and mindmap page layouts to avoid the Fumadocs rendering issues that were breaking processed repository pages

Testing

• npm run build
• verified ?lang=en repo pages render English labels like Repository Wiki, Project Architecture, Export Docs, and Table of Contents
• verified missing-document pages render locale-aware copy and the homepage filter shows All Languages