feat: role-aware nav icons across feed, host, and admin pages

Feed: shows star icon (→ /host) for host/admin, shield icon (→ /admin)
for admin only, alongside the existing account icon.
Host: shows shield icon (→ /admin) for admin only next to "Zur Galerie".
Admin: replaces "Host-Dashboard" text link with star icon (→ /host).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/routes/host/+page.svelte

@@ -202,7 +202,16 @@
 					<p class="text-sm text-gray-500">{event.name}</p>
 				{/if}
 			</div>
-			<a href="/feed" class="text-sm text-blue-600 hover:underline">Zur Galerie</a>
+			<div class="flex items-center gap-3">
+				{#if myRole === 'admin'}
+					<a href="/admin" class="text-gray-400 hover:text-gray-600" aria-label="Admin Dashboard">
+						<svg xmlns="http://www.w3.org/2000/svg" class="h-6 w-6" fill="none" viewBox="0 0 24 24" stroke="currentColor" stroke-width="1.5">
+							<path stroke-linecap="round" stroke-linejoin="round" d="M9 12.75 11.25 15 15 9.75m-3-7.036A11.959 11.959 0 0 1 3.598 6 11.99 11.99 0 0 0 3 9.749c0 5.592 3.824 10.29 9 11.623 5.176-1.332 9-6.03 9-11.622 0-1.31-.21-2.571-.598-3.751h-.152c-3.196 0-6.1-1.248-8.25-3.285Z" />
+						</svg>
+					</a>
+				{/if}
+				<a href="/feed" class="text-sm text-blue-600 hover:underline">Zur Galerie</a>
+			</div>
 		</div>
 	</div>