fix: make edit plan buttons sticky at bottom

app/templates/plan_edit.html

@@ -2,6 +2,21 @@
 
 {% block title %}编辑方案 - 钢琴练习方案系统{% endblock %}
 
+{% block page_css %}
+<style>
+.edit-plan-footer {
+    display: flex;
+    justify-content: flex-end;
+    gap: 0.5rem;
+    padding: 1rem;
+    border-top: 1px solid #dee2e6;
+    background: #f8f9fa;
+    position: sticky;
+    bottom: 0;
+}
+</style>
+{% endblock %}
+
 {% block content %}
 <div class="d-flex justify-content-between align-items-center mb-4">
     <h4><i class="bi bi-edit"></i> 编辑方案</h4>
@@ -41,7 +56,7 @@
             </div>
         </div>
     </div>
-    <div class="card-footer">
+    <div class="edit-plan-footer">
         <button type="button" class="btn btn-secondary" onclick="location.replace('/plan/{{ plan_id }}')">取消</button>
         <button type="button" class="btn btn-primary" onclick="savePlanContent()">
             <i class="bi bi-save"></i> 保存