Add logo to mobile sidebar header (#33)

Author: soonduck-dreams

src/main/resources/templates/fragments/_sidebar.html

@@ -41,6 +41,8 @@
     <div class="offcanvas offcanvas-start" tabindex="-1" id="sidebarOffcanvas">
         <div class="offcanvas-header">
             <div class="d-flex align-items-center gap-2">
+                <img th:src="@{/images/saerok-admin-icon.png}" src="/images/saerok-admin-icon.png"
+                     alt="새록 어드민 로고" width="32" height="32" class="flex-shrink-0">
                 <h5 class="offcanvas-title mb-0">새록 어드민</h5>
                 <span class="environment-badge"
                       th:if="${environmentProfileBadge}"