feat: festive Chinese red background and prize config unification

- Change all big screen backgrounds to pure Chinese red (#c41230)
- Remove vignette effect for consistent display on different screens
- Unify all prize data to match prizes.json configuration
- Add demo participants fallback when no data imported
- Fix particle visibility reset in startGalaxy()

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

packages/shared/src/types/admin.types.ts

@@ -140,10 +140,10 @@ export interface PrizeConfig {
 }
 
 export const PRIZE_CONFIG: PrizeConfig[] = [
-  { round: 1, level: '特等奖', name: 'iPhone 16 Pro Max', winnerCount: 1 },
-  { round: 2, level: '一等奖', name: 'iPad Pro', winnerCount: 3 },
-  { round: 3, level: '二等奖', name: 'AirPods Pro', winnerCount: 5 },
-  { round: 4, level: '三等奖', name: '京东卡 500元', winnerCount: 10, zodiacFilter: 'horse' },
+  { round: 1, level: '第一轮抽奖', name: '幸运伴手礼', winnerCount: 7 },
+  { round: 2, level: '第二轮抽奖', name: '幸运伴手礼', winnerCount: 3 },
+  { round: 3, level: '第三轮抽奖', name: '幸运伴手礼', winnerCount: 4 },
+  { round: 4, level: '第四轮抽奖', name: '幸运伴手礼', winnerCount: 1, zodiacFilter: 'horse' },
 ];
 
 // Default programs for voting
@@ -175,9 +175,9 @@ export const INITIAL_ADMIN_STATE: AdminState = {
   lottery: {
     round: 1,
     subPhase: 'IDLE',
-    prizeLevel: '特等奖',
-    prizeName: 'iPhone 16 Pro Max',
-    winnerCount: 1,
+    prizeLevel: '第一轮抽奖',
+    prizeName: '幸运伴手礼',
+    winnerCount: 7,
     currentWinners: [],
   },
   music: {