feat(showcase): add public showcase page with per-profile/per-postcard visibility controls

app/templates/settings.html

@@ -5,6 +5,13 @@
     <h1>用户设置</h1>
 </div>
 
+<div class="form-card" style="margin-bottom:1.5rem">
+    <div style="display:flex;align-items:center;justify-content:space-between">
+        <h3>展示设置</h3>
+        <a href="/showcase/manage" class="btn btn-primary btn-sm">全局展示设置</a>
+    </div>
+</div>
+
 {% if success %}
 <div class="alert alert-success">{{ success }}</div>
 {% endif %}