feat: add trilingual /about page with generateMetadata and footer link

[HirenGajjar]

Closes #29

Adds src/app/[lang]/about with full trilingual support (EN/FR/DE) and updates the footer.

---

What's new

src/app/[lang]/about/page.tsx — new file

A server component (no "use client") with four sections:

1. Mission — what Clarvia does, the problem it solves, the source-backed approach
2. Legal identity — CLARVIA ASBL, RCS Luxembourg F15680, founders, address, founding date
3. How it works — structured data, multilingual checklists, open-source infrastructure
4. Governance and transparency — links to GOVERNANCE.md, CONTRIBUTING.md, and GitHub org

src/app/[lang]/sections/FooterSection.tsx — updated

Added About link to the footer nav array between Home and Share your experience.

---

Technical decisions

Server component over "use client": The issue requires generateMetadata() which cannot be exported from a client component. The about page has no client-side interactivity, so a server component is the correct and cleaner choice. lang is read from params directly, matching the layout.tsx pattern.

generateMetadata(): Page-specific title and description in all three languages, with correct canonical URLs (/en/about, /fr/about, /de/about) and OpenGraph metadata.

ARIA: All four sections use aria-labelledby pointing to their h2 ids. Header matches the ARIA pattern from PR #19.

Content: Uses Gunther (no umlaut) per issue guidance. Legal name is CLARVIA ASBL throughout.

---

Verified

• /en/about, /fr/about, /de/about all render correctly
• Language switcher active state correct on each
• Footer About link present and working
• npm run lint — 0 errors
• npm run build — passes, all 3 routes statically generated
• Trailing newlines on both files
• 2 files changed, 287 insertions

[TommiLindfors]

Reviewed — this is outstanding work @HirenGajjar. The server component decision is exactly right (generateMetadata can't be exported from a client component), and the ARIA labels on every section are consistent with your earlier PR #19. Full trilingual content, legal details correct, governance links all pointing to the right files.

Note: there will be a small merge conflict with PR #30 (updates page) since both PRs add a footer link. We'll handle that on our side after merging yours.

[TommiLindfors]

Merged! Nine PRs now @HirenGajjar. The about page is exactly what the project needed — proper legal identity, governance links, and the server component decision was the right call. First time a contributor has built a full page for Clarvia.