Build Phase 2 judge vertical slice

.env.example

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+DATABASE_URL=postgres://onlinejudge:onlinejudge@localhost:5433/onlinejudge
+REDIS_URL=redis://localhost:6380
+JUDGE_SERVER_URL=http://localhost:8081
+JUDGE_SERVER_TOKEN=oj2-dev-token
+JUDGE_CONCURRENCY=2
+OJ2_DEV_USERNAME=student
+OJ2_DEV_PASSWORD=student123