fix: 移除早间简报功能 + 修复多处"人机感"用语

- 删除 briefing_handler.go / briefing_store.go 及所有相关路由与配置
- 移除 Gateway Config 中 ToolEngineURL / BriefingTime 字段
- 移除 DevTools 中 gateway 的 TOOL_ENGINE_URL 环境变量
- webhook 错误提示从"AI 服务异常/暂不可用"改为昔涟自然口吻
- markdown 导出中昔涟头像从 🤖 改为 💫
- 后台思考提示词"系统会误解析"改为"我会误解析"

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

devtools/src/config.js

@@ -100,7 +100,6 @@ export const SERVICES = {
       JWT_SECRET: process.env.JWT_SECRET || 'dev-secret-key-change-me',
       AI_CORE_URL: 'http://localhost:8081',
       MEMORY_SERVICE_URL: process.env.MEMORY_SERVICE_URL || 'http://localhost:8091',
-      TOOL_ENGINE_URL: process.env.TOOL_ENGINE_URL || 'http://localhost:8092',
       ADMIN_USERNAME: process.env.ADMIN_USERNAME || 'admin',
       ADMIN_PASSWORD: process.env.ADMIN_PASSWORD || 'cyrene-dev-admin',
       REGISTRATION_ENABLED: process.env.REGISTRATION_ENABLED || 'true',