fix: move vercel config to root, use pnpm

apps/blog/src/content/posts/hello-world.md

@@ -1,5 +1,5 @@
 ---
-title: Hello World
+title: hello world
 date: 2026-01-01
 ---
 

apps/blog/src/content/posts/second-post.md

@@ -1,6 +1,6 @@
 ---
-title: My Second Post
-date: 2025-01-02
+title: my second post
+date: 2026-01-02
 ---
 
 Another post to test the listing.

apps/blog/vercel.json

@@ -1,5 +0,0 @@
-{
-  "buildCommand": "cd apps/blog && npm install && npx astro build --remote",
-  "outputDirectory": "apps/blog/dist",
-  "installCommand": "echo 'skipping root install'"
-}

vercel.json

@@ -0,0 +1,4 @@
+{
+  "buildCommand": "pnpm --filter @ily/blog build --remote",
+  "outputDirectory": "apps/blog/dist"
+}