feat: add french translation for the community/ documentation

[MaximeNzo]

Added French (fr) localization for the Community section (and shared i18n)

Summary

• Add a full French translation of the Community area under docs/fr/community/, including the overview (README), roadmap and publications, FAQs, tools (e.g. CI/CD, testing, pragmatic REST, cybersecurity, code quality), standards (guide, versioning, invariants, triaging bugs, creating new features), contributing (CLA, code of conduct, contributors guide, design review, CVD, change processes, product engineering, new contributor checklist), documentation helpers (API documentation, style guide, standards index), and archive material (discussion-docs such as cross-border, workbench, versioning draft, performance/PSIP/code-improvement projects, ISO/decimal/aws tagging, etc., plus notes where translated).
• Configure VuePress with locale-specific navigation, sidebar, and language selector for English (/) and French (/fr/), including a French Community sidebar that mirrors the English structure with translated titles.
• Add a locale-aware 404 page that shows French copy and links when the path is under /fr/.
• Implement automatic language detection in enhanceApp.js so French-preference browsers are redirected to the /fr/ equivalent of the current page on first visit.
• Update diagrams and illustrations referenced from French Community pages so labels and terminology match the French docs where those assets are localized.
• Fix relative image and asset paths in French Community files to account for the extra directory depth compared to docs/community/... (for example docs/fr/community/...).

Test plan

• Verify the language dropdown appears and switching between English / Français works.
• Navigate through French Community sidebar pages (tools, standards, contributing, documentation, archive) and confirm content renders; images and diagrams load.
• Click TOC / in-page anchors on longer pages (e.g. standards guide, discussion docs) and confirm scrolling / deep links work.
• Visit a non-existent URL under /fr/community/ and confirm the French 404 page.
• Open the site in a French-language browser (or simulate navigator.language) and confirm auto-redirect to /fr/ on first visit where appropriate.
• Spot-check English Community pages remain unchanged and still render correctly.

[kayiganwa04]

Great work @MaximeNzo can be merged.