fix(web): /projects rewrite 在空 API_PATH_PREFIX 配置下被文件路由遮挡——静默失效的假绿

## 发现经过

PR #920 独立复核时定位：复核环境（`NEXT_PUBLIC_API_PATH_PREFIX` 为空串的同源代理配置）下
`/projects` 页面顶部出现红字 `Unexpected token '<', "

Start in apps/web/next.config.mjs around line 144 and apps/web/app/projects/page.tsx; reproduce the issue with an empty NEXT_PUBLIC_API_PATH_PREFIX and inspect the /projects response. Done means the rewrite no longer collides with the filesystem route in that configuration and the page uses the repository's structured dep-failed StateShell wording instead of the raw parse exception.

Written by the indexing model from the issue text.