Serve error-404.html as the Vercel 404 page (#2748)

Co-authored-by: Cursor <cursoragent@cursor.com>

.changeset/preview-vercel-404.md

@@ -0,0 +1,5 @@
+---
+"@tabler/preview": patch
+---
+
+Fixed Vercel deployment to serve `error-404.html` as the custom 404 page.

preview/vercel.json

@@ -1,5 +1,15 @@
 {
-  "redirects": [
-    { "source": "/marketing", "destination": "/marketing.html", "permanent": true }
+  "routes": [
+    {
+      "src": "/marketing",
+      "status": 308,
+      "headers": { "Location": "/marketing.html" }
+    },
+    { "handle": "filesystem" },
+    {
+      "src": "/(.*)",
+      "status": 404,
+      "dest": "/error-404.html"
+    }
   ]
 }