Fix Vercel deployment hanging issue

Added directUrl configuration to Prisma schema and created vercel.json
with extended timeout settings to resolve deployment hangs after database
check. Includes comprehensive deployment guide for Supabase setup.

vercel.json

@@ -0,0 +1,8 @@
+{
+  "functions": {
+    "api/**/*.js": {
+      "maxDuration": 300
+    }
+  },
+  "buildCommand": "npm run build-db && npm run build"
+}