SPONSOR-03 - Expose Sponsors API Endpoint

[oorjagandhi]

Description

Expose a GET endpoint for the Sponsors collection in Payload CMS so the frontend can fetch sponsor data for the Sponsors page. The endpoint needs to support both the sponsor grid and the Sponsor of the Week component.

Acceptance Criteria

• A GET endpoint exists for sponsors (e.g. /api/sponsors)
• The response includes: name, logo, websiteURL, isSponsorOfTheWeek, promoLine, and description for each sponsor
• The isSponsorOfTheWeek boolean is present so the frontend can identify the featured sponsor without a separate request
• Response shape is documented and shared with the frontend team before SPONSOR-02 - Sponsor Grid & Bottom CTA (frontend) #46 is connected