feat(转换能力): 完善PDF转换与链接保留，优化大型文档处理，新增转换提示

assets/webui/index.html

@@ -590,6 +590,10 @@
 						<dd id="metaFonts">0</dd>
 					</div>
 				</dl>
+				<details id="conversionNotice" class="conversion-notice" hidden>
+					<summary>转换提示</summary>
+					<div id="conversionWarnings" class="attachment-detail"></div>
+				</details>
 				<section id="securityPanel" class="security-panel" aria-labelledby="securityPanelTitle" hidden>
 					<div class="panel-row"><div id="securityPanelTitle" class="panel-title compact">安全</div><div class="panel-actions"><button id="encryptSaveButton" class="small-button" type="button" title="加密另存" aria-label="加密另存" aria-haspopup="dialog" aria-controls="exportPanel" disabled>加密</button><button id="signButton" class="small-button" type="button" aria-haspopup="dialog" aria-controls="signPanel" disabled>签章</button><button id="verifyButton" class="small-button" type="button" aria-haspopup="dialog" aria-controls="verifyPanel" disabled>验签</button></div></div>
 					<dl class="meta-list"><div><dt>加密</dt><dd id="securityEncryption">未加密</dd></div><div id="securityMethodRow" hidden><dt>算法</dt><dd id="securityMethod"></dd></div></dl>