refactor(请求): 去掉 axios，所有请求统一从 authFetch 出门；换 token 时断网不再平白弹登录框

utils/api 改成基于 authFetch 的一层 fetch 封装，调用方用法不变；下载测试点也走
authFetch，token 过期时会换一张重试。换 token 那一步断网时，AI 流式接口和自学上报
原来会拿掉 token 重发、弹登录框，现在和普通请求一样报「网络异常」。

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/web/package.json

@@ -26,7 +26,6 @@
     "@vueuse/router": "^15.0.0",
     "@wangeditor-next/editor": "^6.5.0",
     "@wangeditor-next/editor-for-vue": "^6.5.0",
-    "axios": "^1.20.0",
     "canvas-confetti": "^1.9.4",
     "chart.js": "^4.5.1",
     "chartjs-chart-wordcloud": "^4.4.5",