chore(wrangler): add not found handling

Author: ryuapp

wrangler.jsonc

@@ -9,7 +9,8 @@
   "compatibility_date": "2025-09-01",
   "assets": {
     "directory": "./dist",
-    "binding": "ASSETS"
+    "binding": "ASSETS",
+    "not_found_handling": "404-page"
   },
   "observability": {
     "enabled": true