Fix award eligibility FK constraint + add country column to round projects

- specialAward.setEligibility: add ensureUserExists() guard and use Prisma
  connect syntax to prevent FK violation on stale session user IDs
- specialAward.confirmShortlist: same ensureUserExists() guard for confirmedBy
- Round projects table: add Country column showing project origin

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/server/services/round-engine.ts

@@ -690,6 +690,7 @@ export async function getProjectRoundStates(
           title: true,
           teamName: true,
           competitionCategory: true,
+          country: true,
           status: true,
         },
       },