feat: [add GTFS Features Adoption Tracker]

[etienne0101]

Summary:

This PR adds the page /metrics/gtfs/features-tracker
It contains an iframe of the GTFS Features Adoption Tracker.

Expected behavior:

Follow up tickets

• Update design to match MobilityData branding (of the original source page)
• Add information and link in the Mobility Database website to make the page discoverable
• Add a feature tracker view to each feature section on gtfs.org
• For a better integration, the .jsx code could be converted into .tsx and moved to this repository.

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Project	Deployment	Actions	Updated (UTC)
mobilitydatabase-web	Ready	Preview, Comment	Apr 16, 2026 1:42pm

[github-actions]

*Lighthouse ran on https://mobilitydatabase-4l6msisi0-mobility-data.vercel.app/ * (Desktop)
⚡️ HTML Report Lighthouse report for the changes in this PR:

Performance	Accessibility	Best Practices	SEO
🟢 100	🟢 94	🟢 96	🟢 100

*Lighthouse ran on https://mobilitydatabase-4l6msisi0-mobility-data.vercel.app/feeds * (Desktop)
⚡️ HTML Report Lighthouse report for the changes in this PR:

Performance	Accessibility	Best Practices	SEO
🟠 88	🟠 87	🟢 96	🟢 100

*Lighthouse ran on https://mobilitydatabase-4l6msisi0-mobility-data.vercel.app/feeds/gtfs/mdb-2126 * (Desktop)
⚡️ HTML Report Lighthouse report for the changes in this PR:

Performance	Accessibility	Best Practices	SEO
🟠 85	🟢 94	🟢 96	🟢 100

*Lighthouse ran on https://mobilitydatabase-4l6msisi0-mobility-data.vercel.app/feeds/gtfs_rt/mdb-2585 * (Desktop)
⚡️ HTML Report Lighthouse report for the changes in this PR:

Performance	Accessibility	Best Practices	SEO
🟢 99	🟠 84	🟢 96	🟢 100

*Lighthouse ran on https://mobilitydatabase-4l6msisi0-mobility-data.vercel.app/feeds/gbfs/gbfs-flamingo_porirua * (Desktop)
⚡️ HTML Report Lighthouse report for the changes in this PR:

Performance	Accessibility	Best Practices	SEO
🟠 80	🟢 94	🟢 96	🟢 100