fix: update admin page button label clarity

Update 'Manage Folders' button text to 'Manage Libraries and Folders'
to better reflect the full functionality of managing both libraries
and scan directories in one place.

templates/admin.templ

@@ -52,8 +52,8 @@ templ Admin(user User) {
 									<div style="color: var(--text-secondary)" class="text-sm">Re-scan existing files and fix metadata</div>
 								</button>
 								<a href="/admin/library" class="btn-secondary p-4 rounded-lg text-left block">
-									<div class="font-medium">Manage Folders</div>
-									<div style="color: var(--text-secondary)" class="text-sm">Add or remove scan directories</div>
+									<div class="font-medium">Manage Libraries and Folders</div>
+									<div style="color: var(--text-secondary)" class="text-sm">Add or remove libraries and scan directories</div>
 								</a>
 							</div>
 						</div>