Create hackathon-detail-design.md (#466)

Author: Davidemulo

app/(landing)/hackathons/[slug]/hackathon-detail-design.md

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+Hackathon Detail Page Redesign
+Issue: #414
+
+Figma Design
+https://www.figma.com/design/EMNGAQl1SGObXcsoa24krt/Boundless_Project-Details?node-id=0-1&t=A1ywRcn60Xyw0X6h-1
+
+This design proposes a cleaner and more professional UI/UX for the hackathon detail page.
+
+Included in the Figma file:
+- Desktop layout
+- Mobile layout
+- Banner / hero placement proposal
+- Redesigned hero section
+- Sticky sidebar card
+- Tab navigation
+- All tab layouts (overview, participants, resources, announcements, submissions, discussions, find team, winners)
+- Loading state
+- Hackathon not found state
+
+Banner Placement Proposal
+The hackathon banner is placed as a full-width hero image at the top of the page, allowing it to visually represent the hackathon and improve page identity.
+
+The sidebar becomes a compact summary card with key information and actions.
+
+Design Goals
+- Simpler UI and improved visual hierarchy
+- Clear primary actions (Join, Submit, View Submission)
+- Consistent spacing and typography
+- Better mobile usability
+- Professional and product-quality look