Fix Live Preview footer placeholder email to not look like a real hardcoded address

DEFAULT_LEGAL_FOOTER_LINES' email was "admin@mk360.de" — the same domain
as the real send address, which read as a hardcoded real value in the
preview rather than an obvious placeholder. Now "kontakt@musterfirma.de",
matching "Musterstraße 12"'s already-fake spirit. Mirrors the same fix
already made on the Payload backend's copy of this constant.

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

app/lib/emailTemplates.ts

@@ -67,12 +67,15 @@ function escapeHtml(s: string): string {
 
 // Live-Preview-only fallback (no real order/company-settings fetch there,
 // see /email-preview/[type]) — the actual send always passes the real
-// seller (company-settings) through buildLegalFooterLines() below.
+// seller (company-settings) through buildLegalFooterLines() below. Email
+// deliberately doesn't match the real admin@mk360.de send address, so this
+// never reads as a hardcoded real value in the preview — it's a visibly
+// fake placeholder, same spirit as "Musterstraße 12".
 export const DEFAULT_LEGAL_FOOTER_LINES: string[] = [
   "einfach produktiv",
   "Musterstraße 12",
   "12345 Musterstadt",
-  "E-Mail: admin@mk360.de",
+  "E-Mail: kontakt@musterfirma.de",
 ];
 
 // Every business email needs an Anbieterkennzeichnung (§5 TMG-equivalent