feat(B4): 友链页脚 Logo 渲染-5主题 img+名称并排,渲染期补基准

- PortalLink 模型已有 logoUrl,渲染缺口在模板:5 套 footer 增 th:if logo 图(url.upload 补基准+alt 名称+lazy)
- 5 套 main.css 增 .link-logo(高20px/contain/垂直居中/过宽截断)
- PortalSsrIT+2 例(有 logo 渲染图/无 logo 纯文字无 link-logo);mvn -o test 260/260 全绿

src/main/resources/templates/themes/default/fragments/footer.html

@@ -8,8 +8,12 @@
             <div class="links-group" th:each="group : ${site.linkGroups}"
                  th:if="${!#lists.isEmpty(group.links)}">
                 <span class="group-name" th:text="${group.groupName}">分组</span>
-                <a th:each="link : ${group.links}" th:href="${link.linkUrl}" target="_blank" rel="noopener"
-                   th:text="${link.name}">链接</a>
+                <a th:each="link : ${group.links}" th:href="${link.linkUrl}" target="_blank" rel="noopener">
+                    <!-- B4 友链 Logo：有 logo 图片+名称并排（渲染期补基准），无 logo 纯文字 -->
+                    <img th:if="${link.logoUrl != null and !#strings.isEmpty(link.logoUrl)}" class="link-logo"
+                         th:src="${url.upload(link.logoUrl)}" th:alt="${link.name}" loading="lazy">
+                    <span th:text="${link.name}">链接</span>
+                </a>
             </div>
         </div>
     </div>