ops: add sitemap.xml, robots.txt, and structured data

[joelpeace48-cell]

Problem

There is no sitemap.xml, no robots.txt, and no structured data. The site is
the discovery surface for a project seeking grants, contributors, and pilot
partners, and it is not discoverable.

What to do

• app/sitemap.ts generating entries from the shared site map module, so new
  routes are included automatically.
• app/robots.ts allowing indexing in production and disallowing it on
  preview deployments — duplicate preview content competing with production
  is a real and easily avoided problem.
• JSON-LD Organization and SoftwareApplication structured data.
• Per-route description metadata; several routes currently inherit the site
  default.

Acceptance criteria

• Sitemap generated from the route module
• Robots allows production, blocks previews
• JSON-LD validates against Google's testing tool
• Every route has its own description

Notes

Good first issue — well-bounded, no dependencies, and Next.js has first-class
file conventions for all of it.

[VitorBernalRodrigues]

Hi! I’d like to work on this issue.

I’ve reviewed the current scope and plan to implement the sitemap and robots metadata routes using Next.js conventions, add the Organization and SoftwareApplication structured data, and ensure route-specific descriptions are covered. I’ll keep preview indexing behavior separate from production and add focused validation for the generated metadata.

[joelpeace48-cell]

HI @peter-j23 , you're assigned, ensure all ci pipelines are green... Next time you create a PR without been assigned to the issue, you will be flagged