feat: close buttons as a red cross in a square; static files revalidated by content, so a release reaches the browser at once

internal/server/web/templates/files.html

@@ -226,7 +226,7 @@
     <button class="btn ghost small" id="vtext" hidden>Редактировать</button>
     <button class="btn ghost small" id="vhex" hidden>Редактировать бинарно</button>
     <button class="btn small" id="save" hidden>Сохранить</button>
-    <button class="btn ghost small close" id="closev">Закрыть</button>
+    <button class="btn ghost small icon close x" id="closev" title="Закрыть" aria-label="Закрыть"><svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.5" stroke-linecap="round"><path d="M18 6 6 18M6 6l12 12"/></svg></button>
     <div class="vmsg muted" id="vmsg"></div>
   </div>
   <div class="vbody">
@@ -261,7 +261,7 @@
 <dialog id="updlg">
   <div class="dlg-h">
     <strong style="flex:1">Загрузка файлов</strong>
-    <button class="btn ghost small close" id="updlg-close">Закрыть</button>
+    <button class="btn ghost small icon close x" id="updlg-close" title="Закрыть" aria-label="Закрыть"><svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.5" stroke-linecap="round"><path d="M18 6 6 18M6 6l12 12"/></svg></button>
   </div>
   <div class="dlg-b" id="updlg-list"></div>
 </dialog>