Remove redundant email display logic in WinnerBadge component.

Simplified the WinnerBadge component by removing the conditional logic for optionally displaying the email when the display name is available. Updated WinnerCard to use display name as the primary label fallback for members, ensuring cleaner and consistent rendering.

frontend/src/components/WinnerCard.jsx

@@ -23,11 +23,14 @@ export default function WinnerCard({
             style={{ ...styles.input, flex: 1 }}
           >
             <option value="">— kein Sieger —</option>
-            {members.map((m) => (
-              <option key={m.id} value={m.id}>
-                {m.email}
-              </option>
-            ))}
+            {members.map((m) => {
+              const dn = ((m.display_name || "").trim() || (m.email || "").trim());
+              return (
+                <option key={m.id} value={m.id}>
+                  {dn}
+                </option>
+              );
+            })}
           </select>
 
           <button onClick={onSave} style={styles.primaryBtn}>