fix: presentation expiresAt — skip empty date, convert YYYY-MM-DD to end-of-day UTC

Empty string sent to Appwrite datetime column was being interpreted as creation
timestamp, making every no-expiry sunum immediately expired. Fix:
- Only include expiresAt in payload when user actually set a date
- Convert date-only string (YYYY-MM-DD) to YYYY-MM-DDT23:59:59.000Z so the
  sunum stays valid for the entire chosen day across all time zones
- Strip empty customerId/notes to avoid empty-string writes

src/app/(auth)/sign-in/components/login-form-1.tsx

@@ -191,11 +191,6 @@ export function LoginForm1({
             </Link>
           </p>
         </div>
-
-        {/* Alt logo — sadece geniş ekranda gizli olan mobil için */}
-        <p className="mt-10 text-xs text-muted-foreground lg:hidden">
-          Emlak CRM · Kovak Yazılım
-        </p>
       </div>
     </div>
   );