refactor: migrate sponsors banner to component with caching, for #363

[stasadev]

The Issue

• feat: add sponsors banner to ddev.com, fixes #339 #363

The sponsors banner has a few problems:

Sponsorship data isn't cached, and there’s no fallback if GitHub is unavailable:

Pressing F5 or moving from page to page causes the whole site to jump:

How This PR Solves The Issue

1. Adds initial cache for all sponsorships during npm run build (so GitHub failure doesn't break it) and then caches fresh data for a day.

2. I tried several ways to make the banner appear immediately. Nothing worked, I asked ChatGPT to refactor it into an Astro component, which stopped the jumping. This was annoying.

Manual Testing Instructions

1. Open https://20250508-stasadev-sponsors-b.ddev-com-front-end.pages.dev/
2. Check that it doesn't jump
3. Open Dev panel (F12)
4. Check network tab for Fetch/XHR requests, it should fetch from GitHub only the first time
5. Check application tab for ddevSponsorshipData in local storage
6. Delete ddevSponsorshipData, open network tab again, and check for new fetch from GitHub

Note: I deleted src/scripts/sponsors-banner.js as not needed.

Automated Testing Overview

Related Issue Link(s)

Release/Deployment Notes

[rfay]

Thanks!