fix(backend): Resolve PgBoss infinite loop issue and cleanup unused files

Backend fixes:
- Fix PgBoss task infinite loop on SAE (root cause: missing queue table constraints)
- Add singletonKey to prevent duplicate job enqueueing
- Add idempotency check in reviewWorker (skip completed tasks)
- Add optimistic locking in reviewService (atomic status update)

Frontend fixes:
- Add isSubmitting state to prevent duplicate submissions in RVW Dashboard
- Fix API baseURL in knowledgeBaseApi (relative path)

Cleanup (removed):
- Old frontend/ directory (migrated to frontend-v2)
- python-microservice/ (unused, replaced by extraction_service)
- Root package.json and node_modules (accidentally created)
- redcap-docker-dev/ (external dependency)
- Various temporary files and outdated docs in root

New documentation:
- docs/07-运维文档/01-PgBoss队列监控与维护.md
- docs/07-运维文档/02-故障预防检查清单.md
- docs/07-运维文档/03-数据库迁移注意事项.md

Database fix applied to RDS:
- Added PRIMARY KEY to platform_schema.queue
- Added 3 missing foreign key constraints

Tested: Local build passed, RDS constraints verified

docs/03-业务模块/RVW-稿件审查系统/00-模块当前状态与开发指南.md

@@ -34,7 +34,7 @@
 
 1. **稿约规范性评估**（11项标准）
    - 文题字数、摘要结构、参考文献、图片DPI等
-   - 基于《中华脑血管病杂志》稿约标准
+   - 基于《中华医学超声杂志》稿约标准
 
 2. **方法学评估**（3部分，20个检查点）
    - 科研设计评估（9个检查点）