fix(server): 413 entity.too.large干净JSON响应+content-length盲区观测(PostHog 09-09韩国413=HTML错误页暴露) + requestTimeout=0根除Grok慢上传408(09-06,渲染超时已有应用层动态上限兜底,不动server.timeout防大文件渲染回退) + Claude Imagine widget无前缀设计令牌补齐(SVG var(--text-warning)等消失根因)

refactor: 遥测日志改为 metadata 透传 + 图表渲染统一 Puppeteer + Debian Bookworm

feat: add widget renderer (chart.js, mermaid) and bump to v2.0.0