revert: 移除 Dockerfile 中的 migration 特定修复逻辑

- Dockerfile 应该保持通用，不针对特定 migration
- migration 文件本身已修复（没有 created_at 列）

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

backend/services/identity-service/Dockerfile

@@ -58,14 +58,7 @@ COPY --from=builder /app/dist ./dist
 RUN echo '#!/bin/sh\n\
 set -e\n\
 echo "Running database migrations..."\n\
-# First try to run migrations normally\n\
-if ! npx prisma migrate deploy 2>&1; then\n\
-  echo "Migration failed, attempting to resolve..."\n\
-  # Try to mark failed migrations as rolled back and retry\n\
-  npx prisma migrate resolve --rolled-back 20251220070000_add_system_seed_user 2>&1 || true\n\
-  echo "Retrying migrations..."\n\
-  npx prisma migrate deploy\n\
-fi\n\
+npx prisma migrate deploy\n\
 echo "Running database seed..."\n\
 npx prisma db seed || echo "Seed completed (or already seeded)"\n\
 echo "Starting application..."\n\