Feat: landing page ssr + seo optimization

[Alessandro100]

Summary:
closes #1554

Make the landing page a server component and apply best practices for SEO discoverability.

Landing Page Changes

• It can now display with Javascript being disabled
• It's setup as SSG -> allows for default caching in Vercel + fast performance
• Lighthouse performance: Desktop 100, Mobile: [80-90] (current state mobile is 50)
• SEO Audit able to see the page (see screenshots)

i18n Changed

• Language is now done mobilitydatabase.org/fr and not fr.mobilitydatabase.org
• More NextJs default setting -> made it possible to prerender static pages in all languages
• Also preferred structure for (google seo)[https://developers.google.com/search/docs/crawling-indexing/url-structure#for-multi-regional-sites]

Follow up tickets

• Making the header more SSR (complex)
• Adjusting the links to be i18n compatible (ex: /fr navigating to /fr/feeds)
• SSR Theme adjustment to avoid the dark mode flashing

Expected behavior:

Explain and/or show screenshots for how you expect the pull request to work in your testing (in case other devices exhibit different behavior).

Testing tips:

Provide tips, procedures and sample files on how to test the feature.
Testers are invited to follow the tips AND to try anything they deem relevant outside the bounds of the testing tips.

Please make sure these boxes are checked before submitting your pull request - thanks!

• Run the unit tests with yarn test to make sure you didn't break anything
• Add or update any needed documentation to the repo
• Format the title like "feat: [new feature short description]". Title must follow the Conventional Commit Specification(https://www.conventionalcommits.org/en/v1.0.0/).
• Linked all relevant issues
• Include screenshot(s) showing how this pull request works and fixes the issue(s)

Build struture

Screaming Spider SEO Auditing Tool

Current MobilityDatabase landing page

New Landing Page

[Copilot]

Pull request overview

This PR migrates the landing page to Next.js Server-Side Generation (SSG) for improved SEO and performance, and restructures internationalization from subdomain-based (fr.mobilitydatabase.org) to path-based (mobilitydatabase.org/fr) routing following Next.js conventions.

Changes:

• Landing page converted to server component with SSG, enabling pre-rendering and better SEO discoverability
• Internationalization restructured to use path prefixes (/fr) instead of subdomains, following Next.js and Google SEO recommendations
• Removed react-helmet-async dependency in favor of Next.js native metadata API

Reviewed changes

Copilot reviewed 30 out of 32 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/proxy.ts	Replaced subdomain-based locale detection with path-based locale routing using Next.js middleware
src/i18n/routing.ts	New centralized routing configuration defining available locales and path prefix behavior
src/i18n/request.ts	Updated to use requestLocale parameter from route segments instead of cookies
src/i18n/navigation.ts	New locale-aware navigation utilities for Next.js App Router
src/i18n/config.ts	Removed (replaced by routing.ts)
src/app/[locale]/page.tsx	New SSG landing page with metadata for SEO optimization
src/app/[locale]/layout.tsx	New locale-aware root layout replacing old layout.tsx
src/app/[locale]/components/HomePage.tsx	Server component version of Home screen with translations
src/app/[locale]/components/SearchBox.tsx	Extracted client-side search functionality from Home page
src/app/screens/Home.tsx	Removed (replaced by HomePage server component)
src/app/context/ThemeProvider.tsx	Fixed SSR hydration issues with theme initialization
src/app/components/Header.tsx	Added SSR safety checks and lazy loading for better performance
src/app/components/ThemeToggle.tsx	Removed direct localStorage access in favor of context state
src/app/App.tsx	Added locale-aware basename for BrowserRouter compatibility
messages/en.json & messages/fr.json	Added translation keys for home and about pages

[Copilot]

The fontSize property is missing from this section's styling, but the previous Typography elements specify font sizes. For consistency and proper semantic heading hierarchy, consider adding an appropriate font size (e.g., fontSize: 18 or fontSize: '1.125rem').

Suggested change

	fontWeight: 700,
	fontWeight: 700,
	fontSize: '1.125rem',

[Copilot]

Line 47-48 contains hardcoded English text that should be moved to the translation file. This text is not internationalized while the rest of the page uses t() for translations. Move this content to messages/en.json and messages/fr.json under the about namespace.

[Copilot]

This line contains hardcoded English text that should be moved to the translation file. While the list items below use t('benefits.*'), the introductory text is not internationalized. Add this text to the translation files for proper i18n support.

Suggested change

	Additional benefits of using the Mobility Database include
	{t('additionalBenefitsIntro')}

[Copilot]

This TODO comment should be converted to a GitHub issue and linked here, or removed if the current implementation is considered acceptable. The current SSR theme handling may cause the "flash of unstyled content" mentioned in the PR description's follow-up tasks.

Suggested change

	// TODO: Revisit theme for best SSR practices
	// Theme is initialized from system preference and persisted via localStorage to
	// provide a consistent experience between server-rendered markup and client-side hydration.

[vercel]

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Project	Deployment	Actions	Updated (UTC)
mobilitydatabase-web	Error		Feb 3, 2026 4:55pm