chore(deps): upgrade to nextjs 16 (#2203)

* chore(deps): upgrade to nextjs 16

* upgraded fumadocs

* ensure vercel uses bun

* fix build

* fix bui;d

* remove redundant vercel.json

apps/docs/source.config.ts

@@ -2,6 +2,11 @@ import { defineConfig, defineDocs } from 'fumadocs-mdx/config'
 
 export const docs = defineDocs({
   dir: 'content/docs',
+  docs: {
+    postprocess: {
+      includeProcessedMarkdown: true,
+    },
+  },
 })
 
 export default defineConfig({