feat: enhance lottery system with participant import and prize config

- Fix ES module import issue in admin.service.ts (require -> import)
- Fix lottery reveal ghosting by hiding name particles on complete
- Add participant import from Excel with tag calculation
- Add prize configuration service with JSON persistence
- Constrain winners overlay to scroll area dimensions
- Fix macOS lsof syntax in stop script
- Add HorseRace view and renderer (WIP)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

packages/client-screen/src/components/PostcardGrid.vue

@@ -3,7 +3,7 @@ import { computed, ref, onMounted, onUnmounted } from 'vue';
 import PostcardItem from './PostcardItem.vue';
 import type { VotingProgram } from '@gala/shared/types';
 
-interface Props {
+export interface Props {
   programs: VotingProgram[];
   columns?: number;
   rows?: number;