fix: converge-server 修复 Vercel Function 路由 404

- 移除 framework: null 和 outputDirectory: '.'
- Vercel 自动检测 api/ 为 Functions 目录并编译 TypeScript
- 新增 public/ 目录满足 Vercel 静态输出检测
- 添加 api/health.ts 到 functions 配置

Author: CodeSky0

apps/@aether/converge-server/public/.gitkeep

@@ -1,13 +1,15 @@
 {
   "$schema": "https://openapi.vercel.sh/vercel.json",
-  "framework": null,
   "installCommand": "pnpm install --frozen-lockfile",
   "buildCommand": "cd ../../.. && node scripts/vercel-build.mjs && pnpm turbo run build --filter=@aether/converge-server",
-  "outputDirectory": ".",
   "functions": {
     "api/ws.ts": {
       "memory": 1024,
       "maxDuration": 300
+    },
+    "api/health.ts": {
+      "memory": 128,
+      "maxDuration": 10
     }
   }
 }