Show a printer icon on the print view button

The "Seitenansicht" link in the project header had text only, while the
other header buttons show an icon plus text.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/app/projects/[projectId]/page.tsx

@@ -60,6 +60,7 @@ import {
   toDistributionBoardInfoDraft,
   type DistributionBoardInfoDraft,
 } from "../../../frontend/components/distribution-board-info-card";
+import { Printer } from "lucide-react";
 import {
   ProjectSettingsModal,
   type ProjectSettingsInput,
@@ -867,10 +868,11 @@ export default function ProjectDetailPage() {
         </div>
         <div className="d-flex gap-2">
           <Link
-            className="btn btn-primary"
+            className="btn btn-primary d-inline-flex align-items-center gap-2"
             href={`/projects/${projectId}/print`}
             target="_blank"
           >
+            <Printer aria-hidden="true" size={16} />
             Seitenansicht
           </Link>
           <button