[sabinem]

Teams can describe their submission, not just link it

• A team at a hackathon wants to hand in more than a repository: slides, a demo video, a few paragraphs on what they built. Organizers and voters need to see all of it.

Before, a submission had a single box that took a link or free-text notes, so teams squeezed everything into it.

Now, a submission stores a repository link, a link to a folder of attachments, and a description. This branch brings those three fields to the frontend.

• Teams get three fields in the submission form: repository link, attachments folder link, and a description with formatting. A new version starts filled in from the previous one, so fixing one link means retyping nothing. Both links must start with https://. A version with all three fields empty is refused.
• Organizers see all three fields on Manage Submissions, for the current entry, any newer draft, and earlier versions. Descriptions are folded behind a toggle so the list stays easy to scan. The CSV download gains an "Attachments" column.
• Anyone viewing a team's page, voters included, sees the final entry's attachments link and full description.
• Every page now renders a submission through one component, SubmissionContent, so all of them make the same call about which links to make clickable. The repository field may hold plain notes from before links were required; those still show as text, never as a link.

Deliberately left out

• The description is not in the CSV. It is formatted text meant to be read on the page, not in a spreadsheet cell.
• The voting screen still shows only team and project. The repository link already reaches it in the data but has never been displayed there; that is a separate decision.
• The backend field is still called result. Renaming it to repository_url is planned for after the hackathon. The frontend already uses the new name and maps it in one place, so the rename will be a one-line change.