Add www.sani.is-a.dev Vercel verification TXT to apex record

Vercel checks _vercel.sani.is-a.dev (registrable domain boundary per PSL)
for verifying www.sani.is-a.dev ownership, not _vercel.www.sani.is-a.dev.
Adds the missing token alongside the existing apex verification value.

domains/_vercel.sani.json

@@ -5,7 +5,8 @@
   },
   "records": {
     "TXT": [
-      "vc-domain-verify=sani.is-a.dev,45c505d7b88defcefefc"
+      "vc-domain-verify=sani.is-a.dev,45c505d7b88defcefefc",
+      "vc-domain-verify=www.sani.is-a.dev,f47279c09de88964db5c"
     ]
   }
 }