feat: add DOCX export endpoint and button with watermark support

app/templates/plan_detail.html

@@ -81,7 +81,10 @@ async function loadPlan() {
                     <button onclick="downloadPDFWithTemplate()" class="btn btn-sm btn-primary">
                         <i class="bi bi-download"></i> 下载PDF
                     </button>
-                    <button onclick="downloadMDWithTemplate()" class="btn btn-sm btn-outline-primary">
+                    <button onclick="downloadDOCXWithTemplate()" class="btn btn-sm btn-outline-primary">
+                        <i class="bi bi-file-word"></i> 下载DOCX
+                    </button>
+                    <button onclick="downloadMDWithTemplate()" class="btn btn-sm btn-outline-secondary">
                         <i class="bi bi-file-markdown"></i> 下载MD
                     </button>
                 </div>
@@ -138,6 +141,12 @@ function downloadMDWithTemplate() {
     window.open(`/api/plans/${currentPlanId}/md${suffix}`, '_blank');
 }
 
+function downloadDOCXWithTemplate() {
+    const templateId = document.getElementById('reportTemplateSelect')?.value;
+    const suffix = templateId ? `?template_id=${templateId}` : '';
+    window.open(`/api/plans/${currentPlanId}/docx${suffix}`, '_blank');
+}
+
 async function loadTemplates() {
     try {
         const resp = await fetch('/templates/templates?type=report');