fix(ticket): keep file picker out of modal shell to stop dialog offset

The hidden file input was appended to the flex-centered modal shell,
becoming a second flex child that pushed the dialog left and exposed
the native file button (theme display rules override [hidden]).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

assets/js/ticket-center-core.js

@@ -276,12 +276,12 @@
    */
   function bindShell(shell, onClick) {
     var ctx = { uploadRoot: null };
+    // 文件选择器保持脱离文档：shell 是 flex 居中容器，挂进去会成为第二个 flex 子项，
+    // 把对话框挤偏并露出原生「选择文件」按钮（主题样式会覆盖 [hidden]）。
     var input = document.createElement('input');
     input.type = 'file';
     input.accept = IMAGE_ACCEPT;
     input.multiple = true;
-    input.hidden = true;
-    shell.appendChild(input);
     input.addEventListener('change', function () {
       var files = Array.prototype.slice.call(input.files || []);
       input.value = '';