oe-backend-prod-hardening

对OpenEvent后端进行生产加固审查。在扫描LLM异味、嘈杂的打印信息、被忽略的异常、仅适用于开发环境的默认设置、回退诊断泄露以及不一致的错误/日志模式时使用；生成一个优先级排序的、适合拉取请求大小的清理计划。

Audit workflow (tight + actionable)

Scan for runtime smells:
- rg -n "print\\(" backend
- rg -n "except Exception\\s*:\\s*(pass)?$" backend
- rg -n "OE_FALLBACK_DIAGNOSTICS|FALLBACK" backend
- rg -n "ENABLE_DANGEROUS_ENDPOINTS" backend
Classify findings:
- User-visible (must not leak diagnostics)
- Ops-visible (structured logs, trace events)
- Dev-only (move to scripts / gated)
Convert into a PR ladder:
- One concern per PR: logging, error handling, config defaults, MCP bootstrap, etc.

Add/maintain items in docs/internal/BACKEND_REFACTORING_PLAN_DEC_2025_ADDENDUM.md.