feat: 将项目从nano重命名为beaver并更新相关配置

- 将所有环境变量前缀从NANO_改为BEAVER_
- 更新README.md文档内容，包括项目介绍、组件说明和快速开始指南
- 修改.gitignore文件，添加auth-portal运行时路径排除规则
- 更新app-instance镜像标签从nano/app-instance改为beaver/app-instance
- 增强技能安全检查器，支持工具前缀白名单功能
- 添加技能草稿重新检查安全性API端点
- 扩展证据选择器，收集工具调用名称用于技能学习
- 改进技能合成器，基于实际调用的工具生成工具提示
- 优化路由超时处理机制，增加重试逻辑
- 更新后端架构文档，添加可视化入口和基础概念说明
- 实现在WebSocket消息中传递工具迭代次数信息

.env.example

@@ -1,18 +1,18 @@
 # Shared values used by the root deployment flow in README.md
 
-PROJECT_ROOT=/home/ivan/xuan/nano_project
-NANO_NET=nano-instance-edge
+PROJECT_ROOT=/home/ivan/xuan/beaver_project
+BEAVER_NET=beaver-instance-edge
 
-NANO_DEPLOY_TOKEN=change-me
-NANO_AUTHZ_INTERNAL_TOKEN=change-me
+BEAVER_DEPLOY_TOKEN=change-me
+BEAVER_AUTHZ_INTERNAL_TOKEN=change-me
 
-NANO_SERVER_IP=203.0.113.10
-NANO_BASE_DOMAIN=203.0.113.10.nip.io
+BEAVER_SERVER_IP=203.0.113.10
+BEAVER_BASE_DOMAIN=203.0.113.10.nip.io
 
-NANO_PROVIDER=openai
-NANO_MODEL=openai/gpt-5
-NANO_API_KEY=sk-xxxxxxxx
-NANO_API_BASE=
+BEAVER_PROVIDER=openai
+BEAVER_MODEL=openai/gpt-5
+BEAVER_API_KEY=sk-xxxxxxxx
+BEAVER_API_BASE=
 
 # Per-instance Beaver backend config. In Docker app-instance this should point
 # to the mounted single-user sandbox config, not to frontend env.
@@ -21,9 +21,9 @@ BEAVER_CONFIG_PATH=/root/.beaver/config.json
 BEAVER_WORKSPACE=/root/.beaver/workspace
 
 # Must be reachable from app-instance containers.
-NANO_AUTHZ_URL=http://nano-authz-service:19090
-NANO_OUTLOOK_MCP_URL=
-NANO_OUTLOOK_MCP_SERVER_ID=outlook_mcp
+BEAVER_AUTHZ_URL=http://beaver-authz-service:19090
+BEAVER_OUTLOOK_MCP_URL=
+BEAVER_OUTLOOK_MCP_SERVER_ID=outlook_mcp
 
 # Must be reachable from auth-portal and authz-service containers.
-NANO_DEPLOY_URL=http://nano-deploy-control:8090
+BEAVER_DEPLOY_URL=http://beaver-deploy-control:8090