fix: SEED01用户状态改为ACTIVE

- SYSTEM状态会被识别为冻结账户
- 必须是ACTIVE才能作为有效推荐人

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

backend/services/identity-service/prisma/seed.ts

@@ -54,7 +54,7 @@ const SYSTEM_ACCOUNTS = [
     accountSequence: 'D25122100000',  // 种子用户 (序号0，真实用户从1开始)
     nickname: '种子用户',
     referralCode: 'SEED01',
-    status: 'SYSTEM',
+    status: 'ACTIVE',  // 必须是 ACTIVE 才能作为推荐人
   },
 ];