Switch order/verification email From to sellerEmail's domain, honor emailFromName/emailFromAddress override

Mirrors the backend's sellerInfo.ts buildFromHeader() change — SMTP
account moved to admin@einfach-produktiv.com, so From can finally point
at sellerEmail itself instead of the fixed admin@mk360.de placeholder.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/lib/alertAdmin.ts

@@ -40,10 +40,10 @@ export async function sendVerificationEmail(to: string, firstName: string, token
   const url = `https://einfach-produktiv.mk360.de/api/account/verify-email?token=${token}`;
   const seller = await getSellerForInvoice();
   await transport.sendMail({
-    // See orderEmail.ts's own comment on why only the display name is
-    // dynamic — the address stays admin@mk360.de until sellerEmail's domain
-    // is confirmed SPF-authorized on the Hostinger account.
-    from: `"${seller?.sellerName ?? "einfach produktiv"}" <admin@mk360.de>`,
+    // See orderEmail.ts's own comment — From now matches sellerEmail
+    // itself since the SMTP account moved to a mailbox on that domain,
+    // and emailFromName/emailFromAddress let an admin override both.
+    from: `"${seller?.emailFromName || seller?.sellerName || "Björn"}" <${seller?.emailFromAddress || seller?.sellerEmail || "hallo@einfach-produktiv.com"}>`,
     replyTo: seller?.sellerEmail || undefined,
     to,
     subject: "Bitte bestätige deine E-Mail-Adresse",